Tuesday, June 18, 2013

Cesarean Scar Pregnancy: Another Complication on the Rise from High Cesarean Rates

Cesarean Scar Pregnancy, Kung 2006

As a follow-up to Cesarean Awareness Month, we have been focusing on some of the rarer possible downstream complications of cesareans.  Today we discuss Cesarean Scar Pregnancies. Warning ─ this one's not for the faint of heart.

Again, I would reiterate that many cesareans are truly life-saving and necessary, and many others are probably prudent.  However, cesareans are not without risks and should not be done lightly. The extremely high cesarean rates in certain areas of this country and around the world has very distinct public health implications, both in the immediate period around the cesarean and for years afterwards. In particular, the long-term implications of cesareans are under-recognized.

We've already discussed abnormal placental implantation (placenta previa, placenta accreta, placenta increta, placenta percreta), which is one of the most significant risks to future pregnancies after cesarean section.  As a follow-up to this, we also discussed placenta previa in more detail. 

Another potential very serious complication of pregnancies after prior cesarean is an ectopic pregnancy in the cesarean scar itself.

Cesarean Scar Pregnancy

An "ectopic" pregnancy is one that implants outside of the uterus.  Most often, ectopic pregnancies are tubal (in the Fallopian tubes), but sometimes they occur outside of uterus in the abdomen, in the cervix, etc.

However, with the rise in cesarean rates, care providers are now seeing an increase in the previously extremely rare situation of an ectopic pregnancy implanting in the cesarean scar. 

 This is called Cesarean Scar Pregnancy, or CSP.

The main symptom is usually vaginal bleeding during early pregnancy; sometimes this is painless and sometimes it is accompanied by significant abdominal pain.  Very high hCG levels are another symptom that raises the suspicion for CSP. However, some women with CSP have no obvious symptoms at first.

Since many pregnancies experience early spotting, most women don't take vaginal bleeding in the first trimester too seriously.  However, women with a prior cesarean and significant bleeding/abdominal pain may want to consider an early vaginal ultrasound, just in case, especially if it is accompanied by very high hCG levels.

A few care providers feel that every women with a prior cesarean should have an ultrasound in very early pregnancy to check for CSP, although this is by no means standard. The downside to this, of course, is that any prenatal testing carries with it potential for false positives and unnecessary worry.

If you do choose to have an ultrasound in early pregnancy after a prior cesarean, certain things should be checked for. According to a recent 2012 review, the following sonographic findings should raise the suspicion level for a Cesarean Scar Pregnancy:
  • No fetal parts in the uterine cavity or cervix
  • A thin myometrial layer between the bladder and gestational sac
  • A triangular-shaped gestational sac
  • A gestational sac that is close to the bladder and uterine wall
  • Presentation of arteriovenous malformation in the area
Because the non-sonographic symptoms are unclear and easy to ignore at first, many cases of CSP go undetected initially. Even when the patient presents with symptoms to a care provider, the diagnosis may be missed; the 2012 review found that about 13% of CSP are missed or misdiagnosed at first.

Thus, some CSP patients only get recognized once the uterus has ruptured and they are in hypovolemic shock.  Many of these patients have to undergo a hysterectomy to stop the bleeding.

Bottom line, the longer a Cesarean Scar Pregnancy continues, the worse the outcome in most cases. Therefore, most resources agree that it's important to recognize and deal with a CSP as early as possible. If the CSP is caught early, outcomes improve and fertility can often be preserved.

Transvaginal ultrasound is usually reasonably accurate for diagnosing CSP, although the diagnosis can still be missed even with ultrasound. Often color flow Doppler imaging is helpful.  Occasionally an MRI may be used if other results are ambiguous.

Prior cesarean is not the only risk factor for Cesarean Scar Pregnancy.  A history of uterine infections and prior D&C procedures are also risk factors, as is a short inter-pregnancy interval after a cesarean.  Treatment with In Vitro Fertilization may also be associated with CSP, although this is not clear. Some authors have speculated that recent uterine suturing technique changes (single-layer, various suture materials) may also have an effect, though there is little data to support or refute this.

Obviously having a prior cesarean scar is the most important risk factor for CSP.

Ethical Dilemmas

When CSP occurs, nearly all clinicians believe that there is little choice but to end the pregnancy because the growing pregnancy will quickly become life-threatening to the mother, and the fetus is extremely unlikely to survive anyhow. This places parents in the very difficult position of having to make a choice to end a pregnancy in order to save the life of the mother.

A few providers have managed a Cesarean Scar Pregnancy expectantly. This has been done for those who object to termination under any circumstances, in parents who hope to avoid the difficult choice to end a pregnancy, or in hopes that the pregnancy will move into the uterus with time and become viable.

Since a Cesarean Scar Pregnancy is rarely sustainable and will often miscarry on its own with time; some parents hope that taking a wait-and-see approach can relieve them of the difficult choice to end a pregnancy. However, this approach does present significant risk to the mother.

There have been a few extremely rare instances of Cesarean Scar Pregnancies that resulted in viable infants. Usually these are pregnancies where the gestational sac grows towards the uterus, eventually becoming mostly intrauterine pregnancies. Even then, most doctors recommend a planned cesarean at 28-30 weeks as a precaution against later uterine rupture, and usually assume that placenta accreta accompanies the CSP (making hysterectomy a distinct possibility).

Continuing the pregnancy in hopes of being the rare exception that results in a live baby is understandable but risks life-threatening complications because uterine rupture is very common as a CSP progresses. The 2012 review notes that patients advised to take a "wait and see" approach often ended up with an emergency hysterectomy and infant death anyhow.

There are no easy choices here. Women need to know that the further a Cesarean Scar Pregnancy progresses, the riskier the outcome. As one study points out:
It is likely that if a developing pregnancy in a caesarean section scar were to continue to the second or third trimesters, there would be a substantial risk of uterine rupture with catastrophic haemorrhage, with a high risk of hysterectomy causing serious maternal morbidity and loss of future fertility. There is also a danger of invasion of the bladder by the growing placenta. A pregnancy that protrudes through the scar, if viable, can implant on other abdominal organs and continue to grow as a secondary abdominal pregnancy.
As a result, women may experience uterine rupture, major hemorrhages, and internal damage to nearby organs. Many lose their fertility permanently via hysterectomy.  Occasionally, women have lost their lives with a Cesarean Scar Pregnancy, although this is very unusual in developed countries now because of the use of ultrasound for early detection.

Clearly, this is a dilemma with far-reaching consequences and there are no easy answers.

Treatment

Cesarean Scar Pregnancy Diagram, Zhang 2012

Most clinicians believe that the only reasonable treatment for a Cesarean Scar Pregnancy is to end the pregnancy, but the best method for that is still being debated.

There are a wide variety of treatments used for CSP, including D&C, systemic methotrexate, local injection of methotrexate, Uterine Artery Embolization, laparoscopic or hysteroscopic surgical treatments, and others. The relative rarity of CSP makes it hard to know which approach is best and therefore the standard of care on this is still evolving.

A 2012 survey of case reports in the medical literature found that there has been a huge variety of treatments for Cesarean Scar Pregnancies, but that many resulted in significant morbidity (44%).  They reviewed the various treatments used and analyzed the results.

According to the 2012 survey, D&C (Dilation and Curettage) was the most common treatment used for CSP, but it was associated with high rate complications (nearly 62%), and often resulted in hemorrhage. The authors concluded that this was not a good choice for treatment of a CSP.

The authors also found that giving methotrexate systemically to the mother was associated with a 62% morbidity rate.  This was because secondary treatments were often needed and these had a high complication rate. The authors recommended against this treatment too.

In Uterine Artery Embolization (UAE), an interventional radiologist inserts a small catheter into an artery in the leg, runs it up to the arteries that feed the uterus, and injects small particles to reduce blood flow to the uterus. UAE had a complication rate of 46%, so the authors recommended against UAE as a single treatment for CSP. However, UAE is often used in conjunction with or after other therapies to help reduce severe bleeding.

Operative hysteroscopy (examination of the inside of the uterus with a fiber-optic tube inserted via the cervix, then surgical intervention as needed) had a much better complication rate of 18%.

Injecting methotrexate directly into the gestational sac was the treatment associated with the least maternal morbidity in the review. When combined with an intramuscular injection of methotrexate, the complication rate was slightly less than 10%. After this injection, the body slowly breaks down the leftover tissues, so treatment must be followed long-term to be sure everything is resolving fully, but there is less need for surgical intervention and all its risks.

One problem was that many care providers did not realize that methotrexate treatment results in a temporary increase in hCG levels, leading them to use secondary interventions that led to complications:
Many of the complications reported in the literature review resulted because clinicians were not aware that increases in hCG concentrations could be expected with the treatment, Dr. Timor-Tritsch noted. 
"Many secondary treatments were triggered not by bleeding, but by the observation of a post-treatment increase the hCG cycle and vascularity," he said. "The treatments often resulted in escalation of the critical situation and often hysterectomy." 
"Knowledge of the naturally occurring increase of the hCG volume in blood vessels with a slow resolution could have avoided a secondary resolution," Dr. Timor-Tritsch said.
Other treatment options include laparotomy or laparoscopy. This is a surgical excision of the gestational sac and repair of the uterus via opening the abdomen up (laparotomy) or doing the surgery through a small hole in the abdomen (laparoscopy).

After a cesarean scar pregnancy, it may take a while for the mother to recover.  Bleeding may continue off and on for quite a while.  Treatment with methotrexate often takes several months to resolve the situation ─ in some reports, it took up to a year. Often follow-up testing is needed.  And of course, emotional support is needed, since the parents have just been through a very difficult ordeal.

Although most women with a CSP do not choose to have another pregnancy, some do. If the CSP was caught early enough and their uterus was able to be preserved, subsequent pregnancy is certainly possible. Researchers generally suggest that the mother wait a good while before trying to conceive again, since closely-spaced pregnancies may be a risk factor for CSP. Furthermore, if methotrexate or other drugs were part of the treatment, it may take a while for all traces of these drugs to be out of the mother's body. So waiting a while before attempting to conceive again may be a good idea.

Although there are risks, outcomes are reasonably good in pregnancies after CSP. Most authors recommend careful early surveillance of a post-CSP pregnancy in case of repeat Cesarean Scar Pregnancy or abnormal placentation. There is a somewhat higher rate of miscarriage and repeat CSP, and the risk for uterine rupture and placenta accreta is also higher. Case reports have occasionally recorded deaths in mother and/or baby due to uterine rupture in a pregnancy after CSP, so careful monitoring of the pregnancy may be appropriate.

Many post-CSP pregnancies are delivered by planned repeat cesarean section because of the perceived potential for uterine rupture, although it is difficult to estimate the actual risk for uterine rupture under these circumstances.  On the other hand, some authors advocate for vaginal birth in order to avoid further scarring of the uterus. The number of pregnancies after prior CSP is so small that it's difficult to draw any conclusions about the best course of action.

Incidence of Cesarean Scar Pregnancy

Although Cesarean Scar Pregnancy is thankfully still rare, it is on the rise, and likely will continue to rise in parallel with cesarean rates.  

Of course, it's important to note that absolute numerical risk of this complication is low. Very few women with prior cesareans experience this complication. Therefore, as an individual mother, it's unlikely that you would experience a cesarean scar pregnancy.

However, from a public health point of view, it's also important to note that the more cesareans that are done world-wide, the more women are susceptible to this problem and the more cesarean scar pregnancies we will see, even while they remain a rare risk for any one individual.  

The incidence of Cesarean Scar Pregnancy (CSP) is difficult to pinpoint because of its relative rarity and the diversity of baseline cesarean rates in various areas.  This is also a fairly new area of research, with mostly case reports rather than population-wide studies.

But its increase can be noted if you look closely at the research.  One 2002 study notes, "Only 19 cases have been reported in the English medical literature since 1966."

However, a 2004 study, only two years later, looked for case reports that were made after 2002, and found 66 new case reports in only two years. A recent 2012 survey of the literature found 751 case reports. Obviously, the incidence appears to be on the rise.

The increase in case reports may be partly due to higher cesarean rates, but also is probably due to increased awareness of CSP and a willingness to document them as a complication of prior cesareans.  But there's little doubt doctors are seeing them in greater numbers than in the past.

Exact numbers will depend on the study and the underlying risk factors of the population, such as how high its cesarean rate is, how many women have been exposed to D&C (another risk factor for CSP), the usual parity of the population etc. Even so, some general numbers can be found.

One review found a rate of 1 cesarean scar pregnancy per 1800 - 2200 normal pregnancies (all pregnancies, prior cesarean or not).  Another study found a similar rate of 1 CSP per 1800 normal pregnancies.

However, that doesn't tell you what your risk for CSP is if you've had a prior cesarean.

An Israeli study found the CSP rate more along the lines of 1 CSP per 3000 normal pregnancies, but this dropped to a rate of 1 CSP per 531 pregnancies in women who had had cesareans in the past.

Rounded up slightly, about 0.2% of women who had cesareans experienced a Cesarean Scar Pregnancy in a later pregnancy.

Interestingly, this is beginning to approach the incidence of uterine rupture in spontaneous labor among women with a prior cesarean (which is generally around 0.4 - 0.5%).

Interestingly, about half the time Cesarean Scar Pregnancy occurred in a woman with only one prior cesarean.  It is not clear from research whether multiple prior cesareans increases the risk for CSP, but it is clear that when CSP does occur, it can happen in women with only one prior cesarean.

That's why preventing every unnecessary cesarean matters.

Conclusion

Cesarean Scar Pregnancy is an extremely serious problem. Although rare, its incidence is on the rise in parallel with the high rate of cesareans being done these days.

Because it is rare, this is not a complication that individual mothers with a history of prior cesarean should lose much sleep over.  However, from a public health point of view, it is a concern.

Because many cesareans are done because of VBAC bans, out of fear of liability, for convenience, as a routine repeat cesarean, or for other questionable indications, the increasing rate of Cesarean Scar Pregnancy is a sadly avoidable nightmare in many cases. 

This is yet another reason why it's so important to care providers to make sure that Vaginal Birth After Cesarean remains accessible, and why they need to prevent as many unnecessary first cesareans as possible.



References


Obstet Gynecol Surv. 2002 Aug;57(8):537-43. Ectopic pregnancy within a cesarean scar: a review. Fylstra DL. PMID: 12187153
Implantation of a pregnancy within the scar of a previous cesarean delivery is the rarest of ectopic pregnancy locations. Only 19 cases have been reported in the English medical literature since 1966. If diagnosed early, treatment options are capable of preserving the uterus and subsequent fertility. However, a delay in either diagnosis or treatment can lead to uterine rupture, hysterectomy, and significant maternal morbidity. Although expectant and medical managements have been reported, termination of a cesarean scar pregnancy by laparotomy and hysterotomy, with repair of the accompanying uterine scar dehiscence, may be the best treatment option.
Hum Reprod Update. 2004 Nov-Dec;10(6):515-23. Epub 2004 Sep 16. Ectopic pregnancies in a Caesarean scar: review of the medical approach to an iatrogenic complication. Maymon R, Halperin R, Mendlovic S, Schneider D, Herman A. PMID: 15375087
...Sixty-six new cases were reported since 2002, possibly reflecting the increasing number of Caesareans currently being performed as well as the more widespread use of the transvaginal scan allowing their earlier detection. Analysis of these women's obstetric history revealed that those at risk for pregnancy in a Caesarean scar appear to have a history of dilatation and curettage, placental pathology, ectopic pregnancy, and IVF. Twenty-one out of 39 for which this information was available (54%) had undergone multiple (> or =2) Caesareans and 13 had previous dilatation and curettage, which might also be an associated factor....
J Ultrasound Med. 2012 Sep;31(9):1449-56. Cesarean scar pregnancy: sonographic and magnetic resonance imaging findings, complications, and treatment. Osborn DA, Williams TR, Craig BM. PMID: 22922626
A cesarean scar (ectopic) pregnancy occurs when a pregnancy implants on a cesarean scar. This condition is an uncommon but potentially devastating occurrence. The incidence is increasing as cesarean deliveries become more common. Early recognition of the salient sonographic findings is critical because a delay can lead to increased maternal morbidity and mortality. Magnetic resonance imaging is a valuable troubleshooting tool when sonography is equivocal or inconclusive before therapy or intervention. Early diagnosis by sonography directs therapy and improves outcomes by allowing preservation of the uterus and future fertility. We review the imaging features, differential diagnosis, complications, and treatment of cesarean scar pregnancies in the first trimester.
J Clin Ultrasound. 2007 May;35(4):212-5. Sonographic diagnosis of cesarean scar pregnancy at 16 weeks. Smith A, Ash A, Maxwell D. PMID: 17366559
Cesarean scar pregnancy is rare. However, there has been a rapid increase in the reporting of such cases in recent years. Most of the cases reported in the literature were diagnosed early in the first trimester. Possible management options proposed are pertinent to an early diagnosis. We present a case of a cesarean scar pregnancy diagnosed at 16 weeks that posed a dilemma with regard to management. The patient subsequently suffered a ruptured uterus, which was preserved at surgery.
J Clin Ultrasound. 2008 Oct;36(8):504-11. doi: 10.1002/jcu.20471. First-trimester diagnosis of cesarean scar ectopic pregnancy. Moschos E, Sreenarasimhaiah S, Twickler DM.  PMID: 18393379
Once considered extremely rare, implantation of a pregnancy within the scar of a previous cesarean section is becoming more common. In fact, its incidence is now higher than that of cervical ectopic pregnancies. We identified 5 cases of ectopic pregnancy implanted in a prior cesarean section scar at our institution since 2004. We outline the criteria for the first-trimester sonographic diagnosis of cesarean scar ectopic pregnancy, including a new sign of lower uterine segment ballooning, which has previously not been reported. Clinicians must have a heightened awareness of this serious and potentially fatal pregnancy complication.
J Ultrasound Med. 2011 Sep;30(9):1179-84. Fertility performance and obstetric outcomes among women with previous cesarean scar pregnancy. Maymon R, Svirsky R, Smorgick N, Mendlovic S, Halperin R, Gilad K, Tovbin J. PMID: 21876087
...METHODS: We conducted a retrospective study in a large tertiary hospital in Israel. The study included 18 women with a diagnosis of cesarean scar pregnancy between 2000 and 2009. RESULTS: The incidence of cesarean scar pregnancy among our parturient patients was 1 per 3000 for the general obstetric population and 1 per 531 among those with at least 1 cesarean delivery. Sixteen were treated primarily with methotrexate. Two were treated primarily by surgery, and 2 more were treated by surgery after failed methotrexate treatment. After cesarean scar pregnancy treatment, 7 women conceived spontaneously, and 1 conceived by in vitro fertilization-intracytoplasmic sperm injection. The remaining 10 (55%) did not wish to conceive again. Two of the women who became pregnant (25%) had recurrent cesarean scar pregnancy. CONCLUSIONS: This study shows encouraging results for fertility performance and obstetric outcomes after treatment of cesarean scar pregnancy. Nevertheless, the risk of recurrent cesarean scar pregnancy is not negligible.
Obstet Gynecol. 2006 Jun;107(6):1373-81. Cesarean scar ectopic pregnancies: etiology, diagnosis, and management. Rotas MA, Haberman S, Levgur M. PMID: 16738166
...Fifty-nine articles that met the inclusion criteria provided data on the clinical presentation, diagnosis, and treatment modalities of 112 cases of cesarean delivery scar pregnancies. TABULATION, INTEGRATION, AND RESULTS: Review of the 112 cases revealed a considerable increase in the incidence of this condition over the last decade, with a current range of 1:1,800 to 1:2,216 normal pregnancies. More than half (52%) of the reported cases had only one prior cesarean delivery. The mean gestational age was 7.5 +/- 2.5 weeks, and the most frequent symptom was painless vaginal bleeding...Expectant management of 6 patients resulted in uterine rupture that required hysterectomy in 3 patients. Dilation and curettage was associated with severe maternal morbidity. Wedge resection and repair of the implantation site via laparotomy or laparoscopy were successful in 11 of 12 patients. Simultaneous administration of systemic and intragestational methotrexate to 5 women, all with beta-hCG exceeding 10,000 milli-International Units/mL required no further treatment. CONCLUSION: Surgical treatment or combined systemic and intragestational methotrexate were both successful in the management of cesarean delivery scar pregnancy. Because subsequent pregnancies may be complicated by uterine rupture, the uterine scar should be evaluated before, as well as during, these pregnancies.
Management of Cesarean Scar Pregnancy

Ultrasound Obstet Gynecol. 2003 Mar;21(3):220-7. First-trimester diagnosis and management of pregnancies implanted into the lower uterine segment Cesarean section scar. Jurkovic D, Hillaby K, Woelfer B, Lawrence A, Salim R, Elson CJ. PMID: 12666214
...The management of Cesarean section scar pregnancies included transvaginal surgical evacuation, medical treatment with local injection of 25 mg methotrexate into the exocelomic cavity and expectant management. RESULTS: Eighteen Cesarean section scar pregnancies were diagnosed in a 4-year period. The prevalence in the local population was 1 : 1800 pregnancies. Surgical treatment was used in eight women and it was successful in all cases. The respective success rates of medical treatment and expectant management were 5/7 (71%) and 1/3 (33%). Five women (28%) required blood transfusion and one woman (6%) had a hysterectomy. CONCLUSIONS: Cesarean section scar pregnancies are more common than previously thought. When the diagnosis is made in the first trimester the prognosis is good and the risk of hysterectomy is relatively low.
Curr Opin Obstet Gynecol. 2011 Dec;23(6):415-21. doi: 10.1097/GCO.0b013e32834cef0c. Caesarean scar pregnancy: a review of management options. Litwicka K, Greco E. PMID: 22011956
...CSP is a type of ectopic gestation associated with a high risk of serious complications. The cause of this condition and the best management are still unclear. However, some medical and surgical treatment modalities have been suggested. The main objectives in the clinical management of CSP should be the prevention of massive blood loss and the conservation of the uterus to maintain further fertility, women's health and quality of life. Current data suggest that expectant management should not be recommended, whereas there are accumulating data suggesting that early diagnosis offers single or combined medical and surgical treatment options avoiding uterine rupture and haemorrhage, thus preserving the uterus and fertility. SUMMARY: No universal treatment guidelines for the management of CSP have been published up to now. The lack of data on the best evidence should encourage any individual case report and further multicentre studies for recommendations establishment.
Clin Perinatol. 2008 Sep;35(3):519-29, x. doi: 10.1016/j.clp.2008.07.003. Placenta accreta and cesarean scar pregnancy: overlooked costs of the rising cesarean section rate. Rosen T.  PMID: 18952019
An unintended consequence of the rising cesarean section rate is abnormal placentation in subsequent pregnancies, leading to the clinical complications of placenta accreta and cesarean scar pregnancies. Both of these clinical entities are associated with high rates of maternal morbidity and mortality. This article reviews the potential mechanisms by which uterine scarring may lead to abnormal trophoblast invasion, the association of cesarean section with placenta accreta and scar pregnancies, current management, and suggestions for future research to reduce the incidence of these potentially devastating complications of pregnancy.
Am J Perinatol. 2010 Feb;27(2):111-20. doi: 10.1055/s-0029-1224874. Epub 2009 Jun 5. Cesarean scar ectopic pregnancy: case series and review of the literature. Sadeghi H, Rutherford T, Rackow BW, Campbell KH, Duzyj CM, Guess MK, Kodaman PH, Norwitz ER. PMID: 19504427
...We present four cases of cesarean scar ectopic pregnancy diagnosed within a 6-month period between 2007 and 2008. Their initial presentations and management are discussed, followed by a review of the published literature summarizing both diagnostic and management recommendations.
BJOG. 2007 Mar;114(3):253-63. Caesarean scar pregnancy. Ash A, Smith A, Maxwell D. PMID: 17313383
...Transvaginal ultrasound and colour flow Doppler provides a high diagnostic accuracy with very few false positives. A delay in diagnosis and/or treatment can lead to uterine rupture, major haemorrhage, hysterectomy and serious maternal morbidity. Early diagnosis can offer treatment options of avoiding uterine rupture and haemorrhage, thus preserving the uterus and future fertility. Management plan should be individually tailored. Available data suggest that termination of pregnancy is the treatment of choice in the first trimester soon after the diagnosis. Expectant treatment has a poor prognosis because of risk of rupture. There are no reliable scientific data on the risk of recurrence of the condition in future pregnancy, role of the interval between the previous caesarean delivery and occurrence of caesarean scar pregnancy, and effect of caesarean wound closure technique on caesarean scar pregnancy. In this article, we aim to find the demography, pathophysiology, clinical presentation, most appropriate methods of diagnosis and management, with their implications in clinical practice for this condition.
J Reprod Med. 2011 Jul-Aug;56(7-8):356-8. Cesarean scar ectopic pregnancy: a case report of failed combination local and systemic methotrexate management requiring surgical intervention. Stevens EE, Ogburn P. PMID: 21838169
BACKGROUND: Cesarean scar ectopic pregnancies have been diagnosed with increasing frequency in the last decade. There is no consensus of management for these pregnancies; however, prior reports have suggested best results using either combination methotrexate therapy or surgical excision. CASE: We present a case of failed systemic and local methotrexate therapy requiring operative management. CONCLUSION: Cesarean scar ectopic pregnancies can have disastrous outcomes, including uterine rupture, massive hemorrhage and maternal death. Although this is the first case to report a failure of the combination therapy, major morbidities did not occur. We believe this is due to our choice of expedient surgical management.
J Obstet Gynaecol. 2012 Oct;32(7):621-3. doi: 10.3109/01443615.2012.698665. Caesarean scar pregnancy: a precursor of placenta percreta/accreta. Sinha P, Mishra M. PMID: 22943704
In the last decade, diagnosis of caesarean scar (CS) pregnancy and abnormal placental invasion has gone up significantly. It appears that the history of previous caesarean section is the predisposing factor common to both conditions. Until now, these are treated as a separate entity and therefore managed differently. Recent available evidence suggests that these are not a separate entity but rather a continuum of the same condition. If the caesarean scar pregnancy is managed expectantly in the 1st trimester, most likely it evolves into placenta accreta. This leads invariably to peripartum hysterectomy for postpartum haemorrhage (PPH) and severe maternal morbidity. Early diagnosis and intervention may give a favourable outcome.
Ultrasound Obstet Gynecol. 2004 Mar;23(3):247-53. Cesarean scar pregnancy: issues in management. Seow KM, Huang LW, Lin YH, Lin MY, Tsai YL, Hwang JL. PMID: 15027012
...METHODS: During a 6-year period, 12 cases of Cesarean scar pregnancy were diagnosed using transvaginal color Doppler sonography and treated conservatively to preserve fertility...RESULTS: The incidence of Cesarean scar pregnancy was 1:2216 and its rate was 6.1% in women with an ectopic pregnancy and at least one previous Cesarean section...Patients were treated as follows: transvaginal ultrasound-guided injection of methotrexate into the embryo or gestational sac (n = 3), transabdominal ultrasound-guided injection of methotrexate (n = 2), transabdominal ultrasound-guided injection of methotrexate followed by systemic methotrexate administration (n = 2), systemic methotrexate administration alone (n = 2), dilatation and curettage (n = 2), or local resection of the gestation mass (n = 1). Eleven of the 12 patients preserved their reproductive capacity; the remaining patient, treated by dilatation and curettage, underwent a hysterectomy because of profuse vaginal bleeding. The Cesarean scar mass regressed from 2 months to as long as 1 year after treatment. Uterine rupture occurred in one patient during the following pregnancy at 38 + 3 weeks' gestational age. CONCLUSION: Ultrasound-guided methotrexate injection emerges as the treatment of choice to terminate Cesarean scar pregnancy. Surgical or invasive techniques, including dilatation and curettage are not recommended for Cesarean scar pregnancy due to high morbidity and poor prognosis.
BJOG. 2011 Aug;118(9):1136-9. doi: 10.1111/j.1471-0528.2011.02891.x. Epub 2011 Apr 12. Transvaginal removal of ectopic pregnancy tissue and repair of uterine defect for caesarean scar pregnancy. He M, Chen MH, Xie HZ, Yao SZ, Zhu B, Feng LP, Wu YP. PMID: 21481146
From December 2009 to April 2010, six patients with caesarean scar pregnancies (CSPs) underwent the transvaginal removal of ectopic pregnancy tissue and repair of a uterine defect. Transvaginal surgery was performed uneventfully in all cases. The operating time ranged from 45 to 80 minutes. Blood loss ranged from 50 to 150 ml. Serum β-hCG (β-subunit of human chorionic gonadotrophin) levels declined to normal levels within a month for all patients, and all patients recovered without complications. Our results show that the transvaginal removal of ectopic pregnancy tissue and repair of the uterine defect is effective, safe, and minimally invasive for patients with CSP.
J Obstet Gynaecol Res. 2007 Dec;33(6):873-7. Three-dimensional ultrasonographic diagnosis and hysteroscopic management of a viable cesarean scar ectopic pregnancy. Ozkan S, CaliÅŸkan E, Ozeren S, Corakçi A, CakiroÄŸlu Y, CoÅŸkun E. PMID: 18001457
...No therapeutic modality is suggested to be entirely efficacious and safe for preserving uterine integrity. We present here a 29-year-old woman with vaginal bleeding and a gestational sac with a viable embryo of 6 weeks of age that was implanted in a cesarean section scar. Serum beta-hCG levels were 16 792 mIU/mL. Following an unsuccessful treatment course of systemic methotrexate, the patient underwent operative hysteroscopy. Minimally invasive hysteroscopic resection of the ectopic gestational mass without major complication appears to be an alternative therapeutic approach with minimal morbidity and preservation of future fertility.
Am J Obstet Gynecol. 2012 Nov;207(5):386.e1-6. doi: 10.1016/j.ajog.2012.09.012. Epub 2012 Sep 17. Bilateral uterine artery chemoembolization with methotrexate for cesarean scar pregnancy. Shen L, Tan A, Zhu H, Guo C, Liu D, Huang W. PMID: 23107082
OBJECTIVE: The objective of the study was to assess the efficacy of uterine arteries embolization (UAE) for the treatment of cesarean scar pregnancies (CSP). STUDY DESIGN: Forty-six women with CSP were identified between March 2008 and March 2010. All of the patients underwent UAE combined with local methotrexate. RESULTS: Forty-five patients were successfully treated. One patient had an emergency hysterectomy after 20 days because of massive vaginal hemorrhage. The mean time until normalization of serum β-human chorionic gonadotrophin was 37.7 days, and the mean time until CSP mass disappearance was 33.3 days. The mean hospitalization time was 10.5 days. The complications were mainly fever and pain, which were alleviated with symptomatic treatment. All 45 patients had recovered their normal menstruation at follow-up. CONCLUSION: Bilateral uterine artery chemoembolization with methotrexate appears to be a safe and effective treatment for CSP and causes less morbidity than current approaches.
Am J Obstet Gynecol. 2012 Jul;207(1):14-29. doi: 10.1016/j.ajog.2012.03.007. Epub 2012 Mar 10. Unforeseen consequences of the increasing rate of cesarean deliveries: early placenta accreta and cesarean scar pregnancy. A review. Timor-Tritsch IE, Monteagudo A. PMID: 22516620
...We reviewed the literature concerning the occurrence of early placenta accreta and cesarean section scar pregnancy. The review resulted in several conclusions: (1) the diagnosis of placenta accreta and cesarean scar pregnancy is difficult; (2) transvaginal ultrasound seems to be the best diagnostic tool to establish the diagnosis; (3) an early and correct diagnosis may prevent some of their complications; (4) curettage and systemic methotrexate therapy and embolization as single treatments should be avoided if possible; and (5) in the case of cesarean scar pregnancy, local methotrexate- and hysteroscopic-directed procedures had the lowest complication rates.
J Reprod Med. 2012 Jan-Feb;57(1-2):61-4. Late-first-trimester cesarean section scar ectopic pregnancy with placenta increta: a case report. Overcash RT, Khackician ZH. PMID: 22324271
...CASE: A 21-year-old, gravida 3 para 2 woman was diagnosed at 13.5 weeks' gestation by pelvic ultrasound and magnetic resonance imaging with a cesarean scar ectopic pregnancy and placenta increta. Surgical removal of the pregnancy via exploratory laparatomy with intraoperative use of vasopressin minimized initial blood loss. However, extraction of the placenta increta resulted in uncontrolled bleeding, requiring a supracervical hysterectomy. CONCLUSION: This is the first case report, to our knowledge, of a late-first-trimester cesarean section scar ectopic pregnancy with placenta increta. Early identification of the ectopic pregnancy may allow for more conservative, nonsurgical management. However, with a more advanced gestational age and placenta increta, surgical management is most appropriate to minimize associated maternal risks. A transverse wedge resection of the implantation site, uterine artery embolization, uterine artery ligation, endovascular balloon catheters, or uterine artery tourniquet may help decrease bleeding during surgical extraction of the pregnancy and placenta increta, and also may prevent a hysterectomy.
Reproductive Outcomes After Cesarean Scar Pregnancy

Hum Reprod. 2007 Jul;22(7):2012-5. Epub 2007 Apr 20. Reproductive outcomes of women with a previous history of Caesarean scar ectopic pregnancies. Ben Nagi J, Helmy S, Ofili-Yebovi D, Yazbek J, Sawyer E, Jurkovic D. PMID: 17449510
...METHODS: The study included those women who received treatment for their Caesarean scar pregnancies between April 1999 and October 2005. Their ability to conceive, the time it took to become pregnant and outcomes of subsequent pregnancies were all recorded. RESULTS: 40 women with Caesarean scar pregnancies were managed in our unit. The uterus was conserved in 38/40 cases. Follow-up data were available in 29/38 (76%) of women. Twenty-four out of 29 (83%) attempted to become pregnant. Twenty-one out of 24 [88%, 95% confidence interval (CI): 75-100] women conceived spontaneously. Twenty out of 21 (95%, 95% CI: 86-100) pregnancies were intrauterine and one woman (5%, 95% CI: 0-14) had a recurrent scar ectopic. Thirteen out of 20 (65%, 95% CI: 44-86) intrauterine pregnancies appeared normal. Nine out of 13 (69%) were delivered by Caesarean section. Seven out of 20 (35%, 95% CI: 14-56) intrauterine pregnancies ended in spontaneous abortions. CONCLUSIONS: Our study shows that reproductive outcomes following treatment of caesarean scar ectopic pregnancies are favourable. The risk of complications including recurrent scar implantation appears to be low.
Obstet Gynecol. 2008 Feb;111(2 Pt 2):541-5. doi:10.1097/01.AOG.0000287295.39149.bd. Recurrent ectopic pregnancy in a cesarean scar. Holland MG, Bienstock JL. PMID: 18239016
BACKGROUND: Ectopic pregnancy in a cesarean scar is a rare but well-recognized potential complication of cesarean delivery. Multiple risk factors exist, including prior uterine surgery, a history of uterine infections such as endomyometritis, and a brief interval between uterine surgery and subsequent conception...CASE: This patient presented for a dating ultrasound examination at 4 6/7 weeks of gestation. Her history was significant for an ectopic pregnancy in her cesarean scar 3 years prior that was managed by surgical resection. The initial ultrasound examination was suspicious for a recurrent ectopic pregnancy in her cesarean scar. The diagnosis was confirmed on repeat ultrasonography at 6 weeks of gestation. She was treated with methotrexate, and the pregnancy resolved without complication. CONCLUSION: Ectopic pregnancy in a cesarean scar is an important diagnosis to consider in a woman who has had a history of cesarean delivery and whose early ultrasonography shows a thin, lower uterine segment or a low implantation site. If the diagnosis is not clear on initial ultrasound examination, the patient should be followed up with serial ultrasound examinations. Once recognized, patients with this complication may be treated either surgically or medically as indicated by the clinical situation.


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Monday, May 27, 2013

Placenta Previa and Prior Cesarean

Illustration of Complete Previa, with the placenta at
the bottom of the uterus, between baby and the cervix.
Image by Sigrid de Rooij,Wikimedia Commons
As a follow-up to Cesarean Awareness Month last month, we are talking about late complications from cesareans.

A cesarean section is surgery, and thus entails the usual immediate risks associated with surgery, including infection, hemorrhage, anesthesia problems, blood clots, and accidental damage to surrounding tissues.  These alone are substantial enough to warrant concern with the current high cesarean rate.

However, what many people don't realize is that a cesarean also has downstream health implications, long after the cesarean is over, particularly in women who have further pregnancies after the cesarean(s).

In particular, the risk for abnormal placentation rises with each successive cesarean. And abnormal placentation has a high risk for poor outcomes.

Today we are going to discuss the most common of the complications, Placenta Previa.

Placenta Previa

Placenta Previa is the term for a placenta that lies over or near the cervix at the bottom of the uterus instead of on the top or sides of the uterus (see diagram). It is a significant complication in pregnancy. The number of previas has increased in recent years in tandem with the rising cesarean rate and other factors.

Placentas usually implant higher in the uterus, either near the top (fundal), or on the sides (anterior/front side, posterior/back side).

A low-lying placenta is a problem because as the pregnancy progresses, the lower uterine segment (LUS) expands and develops and the cervix begins to thin. This can cause a part of the placenta to shear off (abrupt) and begin to bleed.

This partial abruption of the placenta is often minor at first, but can become major later on, endangering both baby and mother. In addition, in some previas the placenta can block the cervix, making vaginal birth dangerous.

Symptoms of previa include painless bleeding after 24 weeks or so of gestation. The most typical presentation of bleeding is around 32 weeks or so, although some previas never experience bleeding episodes at all. Elevated maternal alpha fetoprotein levels during prenatal testing may also be a sign of a possible previa.

 Any woman who experiences bleeding episodes after about 20 weeks should be evaluated by a care provider.

If you are diagnosed with Placenta Previa, it is important for you to learn more about the condition so you can become a partner in your own care decisions.  In addition, it is very helpful to reach out to a support group so that you can get support as you deal with the previa experience.

If You Are Diagnosed with Placenta Previa

A transvaginal ultrasound is by far the best method of checking placental placement if previa is suspected. Research shows that a number of previas suspected with abdominal ultrasound are able to be ruled out with transvaginal ultrasound.


There are four grades of severity in previas:
  • Type One - placenta is near but not touching mouth of cervix (low-lying placenta)
  • Type Two - placenta reaches mouth of the cervix but doesn't cover it (marginal previa)
  • Type Three - placenta partially covers the mouth of the cervix (partial previa)
  • Type Four - placenta completely overlays the mouth of the cervix (complete or total previa)
It's important to note that a placenta can look low-lying in early pregnancy but "move up" in the uterus as the uterus grows and develops during pregnancy.

Most borderline previas in early or mid-pregnancy completely resolve by the end of pregnancy, or move up enough that the risk is lessened. 

Thus, it's important not to panic if you are told you have a previa early in pregnancy.  Most of the time it just bears watching and will resolve.

However, some never do resolve. This is called a persistent previa. A complete previa where the mouth of the cervix (the os) is completely covered is the most likely to persist until delivery, although it should be noted that some of these do resolve by term.

Posterior previas are less likely to resolve than anterior previas.  A prior cesarean has been shown to be a strong independent risk factor for a persistent previa. Complete previas that are very symmetrically over the os are also likely to persist to term.

All women with significant placenta previa should be evaluated for the possibility of Placenta Accreta (an abnormally adherent placenta) or Vasa Previa (where fetal blood vessels are situated in the membranes over the cervix without the protection of the cord or placenta). Women with a history of cesareans, D&Cs, or in-vitro fertilization should be particularly evaluated for these conditions.

Most of the time, previas completely resolve by term and labor proceeds normally. If the previa is still there by 35 weeks but is minor (2 cm or more from the os), vaginal birth is quite possible, and has a good success rate.

Some providers will also allow women with previas that are 1-2 cm from the os to try for vaginal birth, whereas others feel this is too risky. Even with a vaginal delivery, however, the mother with a marginal or low-lying placenta still needs to be watched carefully for postpartum hemorrhage.

If the placenta is very near or overlays the os at all by 35 weeks, then delivery needs to be by cesarean in order to prevent hemorrhage when the cervix begins to thin and dilate.  Although regional anesthesia (epidural or spinal) can be used, many providers prefer general anesthesia because of the unpredictability of surgery length and the potential for emotional trauma if complications occur.  Some providers start with regional anesthesia to minimize fetal exposure to drugs, then convert to general anesthesia after the baby is delivered.

A cesarean for an anterior previa is a difficult surgery with the potential for major hemorrhage because it can mean cutting through the placenta itself in order to get to the baby.  Many OBs decide to avoid the placenta altogether by doing a high vertical or transverse fundal incision instead, because this may lessen bleeding and make it easier if a hysterectomy is needed. However, it can also mean a more difficult recovery. Discuss the pros and cons of each choice with your provider ahead of time.

Postpartum, previa mothers need to be monitored for hemorrhage, infection, and anemia. In some mothers who experience very severe hemorrhage, milk supplies are impaired and the pituitary gland can be damaged (Sheehan's Syndrome).  Hypothyroidism and adrenal fatigue issues can occur secondary to Sheehan's Syndrome and should be monitored for carefully for years, as symptoms may not become clear until long after the birth.

Postpartum, some mothers have a tough time coping emotionally or may not feel they have enough emotional support after a difficult experience. Many find their experiences dismissed or shrugged off as if a healthy baby is the only thing that matters.  It's important to know that emotional support is available through Sidelines, ICAN, Solace for Mothers, and many other organizations.

Risks Associated with Placenta Previa

Although many women with previas have reasonably good outcomes, previas are associated with an increased risk of a number of complications.

The risk of hemorrhage is the most important of these complications. One study found that nearly 60% of women with previa experienced a significant hemorrhage, and nearly 12% required a blood transfusion.

However, a lot depends on how severe the previa is and whether it detaches normally. Women with low-lying previas (type 1), for example, had only a 7.6% rate of hemorrhage.  As you might expect, women with complete previas tend to have worse outcomes than those with more marginal previas, as would those who also have an accreta (abnormally adherent placenta).

Because of the risk of hemorrhage, it's important to have adequate blood products on hand at a previa birth. Women with a possible previa should try to boost their iron status during pregnancy in order to minimize the impact of significant blood loss during the birth, should it occur.

Women with high hemoglobin levels may want to look into donating and banking their own blood ahead of time in case a transfusion is needed.  They may also want to inquire about the possibility of recycling and re-using any of their blood lost during the cesarean.

In addition to bleeding, the risk for postpartum infection may be higher in women with previas. In some cases, hemorrhage or infection makes a hysterectomy necessary, thus ending the woman's fertility forever. Some sources even recommend a prophylactic cesarean hysterectomy as a precaution, especially if an accreta is also suspected. Multiple prior cesareans increase the chance that a hysterectomy may be needed.

Because the placenta (the source of oxygen and food for the baby) often begins to pull away from the lower uterine segment as pregnancy progresses, the baby in a previa pregnancy is endangered.  It often must be born prematurely and as a result, may need care in the Neonatal Intensive Care Unit (NICU).

Some studies (but not all) show an increase in the rate of Intrauterine Growth Retardation (IUGR) in babies of previa pregnancies. And the rate of perinatal mortality is three to four times higher in a previa pregnancy.  However, many babies of a previa pregnancy do just fine.

If you are diagnosed with a previa, complete pelvic rest will be prescribed (no sex, nothing in the vagina, no pelvic exams, etc.).  Bed rest is common, or at least restrictions from vigorous activity.

Some women with significant bleeding episodes are hospitalized until the baby is delivered, whereas others can be monitored as outpatients. Medicine to prevent premature labor and steroids to mature the baby's lungs early may be given if early delivery looks likely.

The optimal delivery time for women with a complete previa is difficult to know. Providers seek to find a balance between the risk of a severe hemorrhage in the mother versus increased problems in the baby from prematurity. A substantial number of complete previas are delivered before 34 weeks because of significant bleeding episodes during pregnancy. However, most previas are able to go longer.

A recent review recommended a delivery around 36-37 weeks in women with complete previa who are not experiencing severe bleeding episodes. Another review recommended delivery at 36 weeks (2 days after administration of steroids for the baby's lungs). However, RCOG (the British version of ACOG) states that women with uncomplicated cases of placenta previa can wait until 38-39 weeks. A lot depends on the circumstances of each individual case and the practices of attending physicians.

Because some studies have found an increased risk for perinatal mortality in deliveries after 37 weeks, the reality in most hospitals these days is that women with complete previas are usually delivered before term and must therefore deal with prematurity issues.

With significant previas, it is important to be in a hospital that specializes in high-risk deliveries so that a specialized team of surgeons, anesthesiologists, and neonatologists are nearby at all times, as well as the capability for major blood transfusions.  The mother needs to be ready for the possibility that a hysterectomy may become necessary.

Although most women with previas will have reasonably good outcomes, previa is definitely a high-risk condition that deserves careful monitoring and a thorough plan for optimizing outcomes.

Placenta Previa and Prior Cesareans

So why is a woman with a prior cesarean at greater risk for a previa?

The answer seems to be related to the damage done to the uterus from the surgery.

Placenta Previa develops when the uterine lining has been damaged somehow and the fertilized egg implants near this damaged area.

As one resource says:
It is hypothesized to be related to abnormal vascularisation of the endometrium caused by scarring or atrophy from previous trauma, surgery, or infection. These factors may reduce differential growth of lower segment, resulting in less upward shift in placental position as pregnancy advances.
Risk factors for developing Placenta Previa include the mother's age, prior cesareans, smoking or drug use, high number of prior pregnancies, closely-spaced pregnancies, prior uterine surgery, pregnancy with multiples, congenital anomalies (birth defects), assisted reproduction technology (assisted fertilization), endometriosis, and prior D&C procedures.

Although multiple risk factors are at work with Placenta Previa, it is clear that cesareans are one of the strongest risk factors.

Even only one prior cesarean raises the risk for previa significantly.  One large study found:
The rate of placenta previa at second birth for women with vaginal first births was 4.4 per 1000 births, compared to 8.7 per 1000 births for women with CS at first birth.
Another study (Getahun 2006) found that the incidence of previa was higher (0.63%) in women whose first birth was by cesarean than in women whose first birth was vaginal (0.38%).

The risk for previa is even higher with multiple prior cesareans.  As Getahun 2006 concluded:
There is a dose-response pattern in the risk of previa, with increasing number of prior cesarean deliveries.
A research review (Ananth 1997) looked at four studies that were able to stratify the relative risk of previa by number of prior cesareans. The relative risks were:
  • 4.5 for one prior cesarean
  • 7.4 for two prior cesareans
  • 6.5 for three prior cesareans
  • 44.9 for four or more prior cesareans
But what does that mean in actual numerical risk?  Most studies only show relative risk, but a few studies do have some hard numbers by number of prior cesareans.  For example, Clark (1985) found the following incidence of previa:
  • unscarred uterus = 0.26% previa
  • 1 c/s = 0.65% previa
  • 2 c/s = 1.8% previa
  • 3 c/s = 3.0% previa
  • 4+c/s = 10.0% previa
Of course, exact numerical risk varies from study to study.  To 1995 found a previa incidence of:
  • 0.75% in women with no prior cesareans
  • 1.22% in women with one prior cesarean
  • 2.11% in women with two or more prior cesareans
In Juntunen 2004, the previa rate was 0.5% in the general population, but was 5.4% among with four or more prior cesareans. Obviously, the exact rate depends on the study, but the trend is clear.  The more cesareans you have had, the greater your risk for developing previa. 

Although parity (number of prior pregnancies) and number of prior cesareans are both risk factors for previa, they interact to increase the risk even more. In Gilliam 2002, a woman who had 4+ pregnancies but only one cesarean had 1.72x the risk for previa, but a woman who had 4+ pregnancies and 4+ cesareans had 8.76x the risk for previa.

And when a previa is present, a history of multiple prior cesareans increases the risk for poor maternal outcome significantly, including transfusion, hysterectomy, operative injury, coagulopathy, venous thromboembolism, pulmonary edema, or death.

This points out the importance of VBAC access and avoiding multiple repeat cesareans whenever possible.

 Unfortunately, that's the exact opposite of the trend in obstetrics these days.

My "Previa" Story

As many readers of this blog know, I had two cesareans and then two VBACs with my children.  What I haven't shared is that I had a previa scare with my third.

In that pregnancy, my placenta implanted in the front of the uterus (anterior), down low and near the scar, although we didn't know it at first. I chose not to have an early ultrasound, so it was not until my ultrasound near the end of the second trimester that we discovered that my placenta was anterior.

Anterior placentas are notorious for making it hard to hear the baby's heartbeat at first. That led to one midwife telling me (in a very callous way) that I had obviously miscarried the pregnancy. Fortunately, a different midwife was later able to find the baby's heartbeat and let me know that the pregnancy was still viable.  But it was an angst-filled time until we were able to know that for sure.

If we'd had an early ultrasound, I might have been able to confirm more easily that the pregnancy was still there despite the anterior placenta blocking the sound of the heartbeat, but we also would have experienced a big scare about placenta previa. That anterior placenta's location over my scars would have caused a lot of worry and panic to us all. By delaying the ultrasound till later, the placenta had "moved up" and we knew that neither previa nor accreta was present.

Although it's always a woman's choice whether or not to have prenatal testing, it may be prudent to consider at least one ultrasound to check placentation in women with a history of cesareans or other uterine instrumentation.

Prenatal testing always comes with pros and cons, but remember, some previas and accretas are not symptomatic before birth, and outcomes are improved if these conditions are discovered before birth.  Therefore, the more cesareans you have had, the more you might want to consider an ultrasound for placental placement. Such testing is never compulsory, mind, but it is probably strongly worth considering in this situation.

However, too many women with prior cesareans are subjected to unnecessary worry and additional testing by early ultrasounds that show a low placenta near the scar. Research shows that 90-95% of previas diagnosed by the second trimester will resolve by term.

So although an ultrasound to check placental placement is a prudent thing to consider in women with prior cesareans, women might want to consider waiting until later in pregnancy to do so unless there is bleeding or other issues that necessitate earlier testing.

Summary

Cesareans are not good or bad in and of themselves. Sometimes they can be life-saving, sometimes they are prudent, sometimes they are a choice. But the cesarean rate in many areas of the world is quite high, and this comes with consequences.

One of the major public health implications of a high cesarean rate is placental complications in subsequent pregnancies after the cesarean. Of these placental issues, Placenta Previa is the most common.

The incidence of Placenta Previa is generally cited in most sources these days as about 1 in 200 to 1 in 250 over the whole pregnant population (0.4 - 0.5%).

However, some earlier studies cite an incidence of between 0.2% to 0.5%. One meta-analysis from the 1990s states:
An examination for trends over time in the incidence of placenta previa revealed that the incidence of this disorder was almost similar until the mid-1980s (1966 to 1974: incidence was 0.36%; 1975 to 1984, 0.37%), but the incidence was 0.48% among studies conducted between 1985 and 1995.
Some studies now place the incidence between 0.5% and 1.5%. However, the prevalence varies greatly from study to study and area to area.  Much depends on the characteristics of the population being studied.

An increase in older mothers, an increased use of D&Cs, increased fertility treatments, and the huge increase in cesarean rates may explain the increased rate of previas in recent years. Yet it's important to note that of these influences, the high cesarean rate may be the most modifiable risk factor. 

The main risk of previa is significant bleeding issues with the placenta as the pregnancy progresses, and especially when the cervix begins to thin and dilate. Previa is associated with a significant risk for severe hemorrhage in the mother and may necessitate blood transfusions or hysterectomy. Although rare, sometimes the mother even dies, especially in third world countries.

In the baby, previa is associated with increased rates of prematurity, respiratory distress, NICU care, and congenital anomalies. The perinatal mortality rate is significantly higher in pregnancies complicated by previa.

When previa occurs, the more prior cesareans a woman has had, the worse her chances for a "morbidly adherent" placenta (an accreta), as well as for major maternal morbidity (hemorrhage, transfusions, blood clot, pulmonary edema, operative injury, hysterectomy, or death).

And the risk doesn't end there. A woman is at higher risk for another previa in future pregnancies after a first previa pregnancy, as well as for another premature birth (even with subsequent normal placentation).

In other words, lower the rate of unnecessary primary and repeat cesareans, and you may prevent quite a number of maternal hysterectomies, severe hemorrhages, premature babies, and perinatal deaths from previa down the road.

Clearly, Placenta Previa is a major potential complication of pregnancies after a prior cesarean. As the authors of one meta-analysis on previa and prior cesareans concluded:
This study provides yet another reason for reducing the rate of primary cesarean delivery and for advocating vaginal birth for women with prior cesarean delivery.
Care providers and hospitals, are you listening?


References

General Information on Placenta Previa
Resources
Placenta Previa Incidence Trends

 Aust N Z J Obstet Gynaecol. 2012 Oct;52(5):483-6. doi: 10.1111/j.1479-828X.2012.01470.x. Epub 2012 Aug 2. Trends and recurrence of placenta praevia: a population-based study. Roberts CL, Algert CS, Warrendorf J, Olive EC, Morris JM, Ford JB. PMID: 22862285
We determined recent trends and recurrence rates of placenta praevia in 790,366 deliveries in NSW. From 2001 to 2009, the rate of placenta praevia increased by 26%, from 0. 69% to 0. 87% (trend P < 0.001). The placenta praevia recurrence rate in a second birth was 4.8%. Two-thirds of the increase in placenta praevia was accounted for by trends in known risk factors, and the unexplained portion may reflect changes in unidentified risk factors or in the threshold for placenta praevia diagnosis.
Placenta Previa Adverse Outcomes

Arch Gynecol Obstet. 2011 Jul;284(1):47-51. doi: 10.1007/s00404-010-1598-7. Epub 2010 Jul 22. Critical analysis of risk factors and outcome of placenta previa. Rosenberg T, Pariente G, Sergienko R, Wiznitzer A, Sheiner E. PMID: 20652281
...RESULTS: During the study period, there were 185,476 deliveries, of which, 0.42% were complicated with placenta previa. Using a multivariable analysis with backward elimination, the following risk factors were independently associated with placenta previa: infertility treatments (OR 1.97; 95% CI 1.45-2.66; P < 0.001), prior cesarean delivery (CD; OR 1.76; 95% CI 1.48-2.09; P < 0.001) and advanced maternal age (OR 1.08; 95% CI 1.07-1.09; P < 0.001). Placenta previa was significantly associated with adverse outcomes such as peripartum hysterectomy (5.3 vs. 0.04%; P < 0.001), previous episode of second trimester bleeding (3.9 vs. 0.05%; P < 0.001), blood transfusion (21.9 vs. 1.2%; P < 0.001), maternal sepsis (0.4 vs. 0.02%; P < 0.001), vasa previa (0.5 vs. 0.1%; P < 0.001), malpresentation (19.8 vs. 5.4%; P < 0.001), postpartum hemorrhage (1.4 vs. 0.5%; P = 0.001) and placenta accreta (3.0 vs. 1.3%; P < 0.001). Placenta previa was significantly associated with adverse perinatal outcomes such as higher rates of perinatal mortality (6.6 vs. 1.3%; P < 0.001), an Apgar score <7 after 1 and 5 min (25.3 vs. 5.9%; P < 0.001, and 7.1 vs. 2.6%, P < 0.001, respectively), congenital malformations (11.5 vs. 5.1%; P < 0.001) and intrauterine growth restriction (3.6 vs. 2.1%; P = 0.003). CONCLUSIONS: Infertility treatments, prior cesarean section, and advanced maternal age are independent risk factors for placenta previa. An increase in the incidence of these risk factors probably contributes to a rise in the number of pregnancies complicated with placenta previa and its association with adverse maternal and perinatal outcomes. Careful surveillance of these risk factors is recommended with timely delivery in order to reduce the associated complications.
Obstet Gynecol. 2007 Dec;110(6):1249-55. Pregnancy outcomes for women with placenta previa in relation to the number of prior cesarean deliveries. Grobman WA, Gersnoviez R, Landon MB, Spong CY, Leveno KJ, Rouse DJ, Varner MW, Moawad AH, Caritis SN, Harper M, Wapner RJ,Sorokin Y, Miodovnik M, Carpenter M, O'Sullivan MJ, Sibai BM, Langer O, Thorp JM, Ramin SM, Mercer BM; National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) Network. PMID: 18055717
...METHODS: Women with a placenta previa and a singleton gestation were identified in a concurrently collected database of cesarean deliveries performed at 19 academic centers during a 4-year period. Maternal and perinatal outcomes were analyzed after stratifying by the number of cesarean deliveries before the index pregnancy. RESULTS:...Multiple measures of maternal morbidity (eg, coagulopathy, hysterectomy, pulmonary edema) increased in frequency as the number of prior cesarean deliveries rose. Even one prior cesarean delivery was sufficient to increase the risk of an adverse maternal outcome (a composite of transfusion, hysterectomy, operative injury, coagulopathy, venous thromboembolism, pulmonary edema, or death) from 15% to 23%, which corresponded, in multivariable analysis, to an adjusted odds ratio of 1.9 (95% confidence interval 1.2-2.9)...CONCLUSION: Among women with a placenta previa, an increasing number of prior cesarean deliveries is associated with increasing maternal, but not perinatal, morbidity.
Am J Obstet Gynecol. 2003 May;188(5):1299-304. The effect of placenta previa on neonatal mortality: a population-based study in the United States, 1989 through 1997. Ananth CV, Smulian JC, Vintzileos AM. PMID: 12748502
...STUDY DESIGN: A retrospective cohort study was performed of live births in the United States (1989-1991 and 1995-1997) that used the national linked birth/infant death records from 22,368,235 singleton pregnancies...RESULTS: Placenta previa was recorded in 2.8 per 1000 live births (n = 61,711). Neonatal mortality rate was 10.7 with previa, compared with 2.5 per 1,000 among other pregnancies (relative risk, 4.3; 95% confidence interval, 4.0,4.8). At 28 to 36 weeks, babies born to women with placenta previa weighed, on average, 210 g lower than babies born to women without placenta previa (P <.001)...CONCLUSION: The risk of neonatal mortality was higher for babies born to women with placenta previa than for babies born to women without placenta previa who were delivered at > or =37 weeks of gestation. Pregnancies that are diagnosed with placenta previa must be monitored carefully, especially as they approach term.
Obstet Gynecol. 1999 Apr;93(4):541-4. Neonatal outcomes with placenta previa. Crane JM, van den Hof MC, Dodds L, Armson BA, Liston R. PMID: 10214830
...METHODS: This was a population-based, retrospective cohort study involving all singleton deliveries in Nova Scotia from 1988 to 1995...RESULTS: Among 92,983 pregnancies delivered during the study period, 305 cases of placenta previa were identified (0.33%). After controlling for potential confounders, neonatal complications significantly associated with placenta previa included major congenital anomalies (odds ratio [OR] 2.48), respiratory distress syndrome (OR 4.94), and anemia (OR 2.65). The perinatal mortality rate associated with placenta previa was 2.30% (compared with 0.78% in controls) and was explained by gestational age at delivery, occurrence of congenital anomalies, and maternal age. Although there was a higher rate of preterm births in the placenta previa group (46.56% versus 7.27%), there was no difference in birth weights between groups after controlling for gestational age at delivery. CONCLUSION: Neonatal complications of placenta previa included preterm birth, congenital anomalies, respiratory distress syndrome, and anemia. There was no increased occurrence of fetal growth restriction.
Am J Obstet Gynecol. 2003 May;188(5):1305-9. Placenta previa: neonatal death after live births in the United States. Salihu HM, Li Q, Rouse DJ, Alexander GR. PMID: 12748503
...DESIGN: This was a population-based retrospective cohort study of 1997 United States singleton live births...RESULTS: Of 3,773,369 live births, 9656 were complicated by placenta previa (2.6 cases per 1000). Among cases of placenta previa, 114 neonatal deaths occurred (11.8 per 1000) versus 14951 (4 per 1000) among non-placenta previa neonates (P <.0001). The adjusted relative risk of death was three times higher among placenta previa neonates (hazard ratio, 3.06; 95% CI, 2.40-3.94). Placenta previa-related death was mediated through preterm delivery rather than small for gestational age. CONCLUSION:Placenta previa triples the rate of neonatal mortality, which is mediated mainly through preterm birth.
Placenta Previa and Prior Cesarean

BMC Pregnancy Childbirth. 2011 Nov 21;11:95. doi: 10.1186/1471-2393-11-95. Risk of placenta previa in second birth after first birth cesarean section: a population-based study and meta-analysis. Gurol-Urganci I, Cromwell DA, Edozien LC, Smith GC, Onwere C, Mahmood TA, Templeton A, van der Meulen JH. PMID: 22103697
...METHODS: Retrospective cohort study of 399,674 women who gave birth to a singleton first and second baby between April 2000 and February 2009 in England...RESULTS: The rate of placenta previa at second birth for women with vaginal first births was 4.4 per 1000 births, compared to 8.7 per 1000 births for women with CS at first birth. After adjustment, CS at first birth remained associated with an increased risk of placenta previa (odds ratio = 1.60; 95% CI 1.44 to 1.76)....
Am J Obstet Gynecol. 1997 Nov;177(5):1071-8. The association of placenta previa with history of cesarean delivery and abortion: a metaanalysis. Ananth CV, Smulian JC, Vintzileos AM. PMID: 9396896
...RESULTS:...The tabulation of 36 studies identified a total of 3.7 million pregnant women, of whom 13,992 patients were diagnosed with placenta previa. The reported incidence of placenta previa ranged between 0.28% and 2.0%, or approximately 1 in 200 deliveries. Women with at least one prior cesarean delivery were 2.6 (95% confidence interval 2.3 to 3.0) times at greater risk for development of placenta previa in a subsequent pregnancy...Four studies, encompassing 170,640 pregnant women, provided data on the number of previous cesarean deliveries. These studies showed a dose-response pattern for the risk of previa on the basis of the number of prior cesarean deliveries. Relative risks were 4.5 (95% confidence interval 3.6 to 5.5) for one, 7.4 (95% confidence interval 7.1 to 7.7) for two, 6.5 (95% confidence interval 3.6 to 11.6) for three, and 44.9 (95% confidence interval 13.5 to 149.5) for four or more prior cesarean deliveries. ...CONCLUSION: There is a strong association between having a previous cesarean delivery, spontaneous or induced abortion, and the subsequent development of placenta previa. The risk increases with number of prior cesarean deliveries. Pregnant women with a history of cesarean delivery or abortion must be regarded as high risk for placenta previa and must be monitored carefully. This study provides yet another reason for reducing the rate of primary cesarean delivery and for advocating vaginal birth for women with prior cesarean delivery.
Obstet Gynecol. 2002 Jun;99(6):976-80. The likelihood of placenta previa with greater number of cesarean deliveries and higher parity. Gilliam M, Rosenberg D, Davis F. PMID: 12052584
...METHODS: A hospital-based, case-control study was conducted in which 316 multiparous women with placenta previa were identified. Controls consisted of 2051 multiparous women with spontaneous vaginal deliveries...RESULTS: Women with a prior cesarean delivery were more likely to have a placenta previa than those without (odds ratio [OR] 1.59, 95% confidence interval [CI] 1.21, 2.08). The likelihood of placenta previa increased as both parity and number of cesarean deliveries increased. Thus, the adjusted OR for a primiparous woman with one cesarean delivery was 1.28 (95% CI 0.82, 1.99). For a woman who has four or more deliveries with only a single cesarean delivery, the OR increases to 1.72 (95% CI 1.12, 2.64). This trend continues with greater parity and a greater number of cesarean deliveries such that the likelihood of placenta previa for a woman with parity greater than four and greater than four cesarean deliveries was OR 8.76 (95% CI 1.58, 48.53). CONCLUSION: This study supports the association between prior cesarean delivery and placenta previa and demonstrates that the joint effect of parity and prior cesarean delivery is greater than that of either variable alone.
Obstet Gynecol. 2006 Apr;107(4):771-8. Previous cesarean delivery and risks of placenta previa and placental abruption. Getahun D, Oyelese Y, Salihu HM, Ananth CV. PMID: 16582111
...METHODS: A retrospective cohort study of first 2 (n = 156,475) and first 3 (n = 31,102) consecutive singleton pregnancies using the 1989-1997 Missouri longitudinally linked data were performed...RESULTS: Rates of previa and abruption were 4.4 (n = 694) and 7.9 (n = 1,243) per 1,000 births, respectively. The pregnancy after a cesarean delivery was associated with increased risk of previa (0.63%) compared with a vaginal delivery (0.38%, RR 1.5, 95% confidence interval [CI] 1.3-1.8). Cesarean delivery in the first and second births conferred a two-fold increased risk of previa in the third pregnancy (RR 2.0, 95% CI 1.3-3.0) compared with first two vaginal deliveries...A second pregnancy within a year after a cesarean delivery was associated with increased risks of previa (RR 1.7, 95% CI 0.9-3.1) and abruption (RR 1.5, 95% CI 1.1-2.3). CONCLUSION: A cesarean first birth is associated with increased risks of previa and abruption in the second pregnancy. There is a dose-response pattern in the risk of previa, with increasing number of prior cesarean deliveries. A short interpregnancy interval is associated with increased risks of previa and abruption.
Obstet Gynecol. 2001 May;97(5 Pt 1):765-9. First-birth cesarean and placental abruption or previa at second birth (1). Lydon-Rochelle M, Holt VL, Easterling TR, Martin DP. PMID: 11339931
...METHODS: We conducted a population-based, retrospective cohort analysis using data from the Washington State Birth Events Record Database. The study cohort included all primiparas who gave birth to live singleton infants in nonfederal short-stay hospitals from January 1, 1987, through December 31, 1996, and who had second singleton births during the same period (n = 96,975)...RESULTS: Among our study cohort, abruptio placentae complicated 11.5 per 1000 and placenta previa 5.2 per 1000 singleton deliveries at second births. In logistic regression analyses adjusted for maternal age, women with first-birth cesareans had significantly increased risk of abruptio placentae (OR 1.3, 95% CI 1.1, 1.5), and placenta previa (OR 1.4, 95% CI 1.1, 1.6) at second births, compared with women with prior vaginal deliveries. CONCLUSION: We found moderately increased risk of placental abruption and previa as a long-term effect of prior cesarean delivery on second births.
BJOG. 2007 May;114(5):609-13. Epub 2007 Mar 12. Association of caesarean delivery for first birth with placenta praevia and placental abruption in second pregnancy. Yang Q, Wen SW, Oppenheimer L, Chen XK, Black D, Gao J, Walker MC. PMID: 17355267
...POPULATION: A total of 5,146,742 singleton second pregnancies were available for the final analysis after excluding missing information...RESULTS: Placenta praevia was recorded in 4.4 per 1000 second-birth singletons whose first births delivered by caesarean section and 2.7 per 1000 second-birth singletons whose first births delivered vaginally...The adjusted odds ratio (95% CIs) of previous caesarean section for placenta praevia in following second pregnancies was 1.47 (1.41, 1.52) after controlling for maternal age, race, education, marital status, maternal drinking and smoking during pregnancy, adequacy of prenatal care, and fetal gender...CONCLUSION: Caesarean section for first live birth is associated with a 47% increased risk of placenta praevia and 40% increased risk of placental abruption in second pregnancy with a singleton.
Obstet Gynecol. 1985 Jul;66(1):89-92. Placenta previa/accreta and prior cesarean section. Clark SL, Koonings PP, Phelan JP. PMID: 4011075
...the records of all patients presenting to labor and delivery with the diagnosis of placenta previa between 1977 and 1983 were examined. Of a total of 97,799 patients, 292 (0.3%) had a placenta previa. The risk of placenta previa was 0.26% with an unscarred uterus and increased almost linearly with the number of prior cesarean sections to 10% in patients with four or more. The effect of advancing age and parity on the incidence of placenta previa was much less dramatic. Patients presenting with a placenta previa and an unscarred uterus had a 5% risk of clinical placenta accreta. With a placenta previa and one previous cesarean section, the risk of placenta accreta was 24%; this risk continued to increase to 67% (two of three) with a placenta previa and four or more cesarean sections....
Int J Gynaecol Obstet. 1995 Oct;51(1):25-31. Placenta previa and previous cesarean section. To WW, Leung WC. PMID: 8582514
...METHOD: The records of all patients delivered with the diagnosis of placenta previa during the 10-year period from 1984 to 1993 were reviewed. RESULTS: From a total of 50,485 deliveries, 421 (0.83%) had placenta previa, 43 (10.2%) of whom had a history of previous cesarean section. The incidence of placenta previa was significantly increased in those with a previous cesarean section (1.31%) compared with those with an unscarred uterus (0.75%) (R.R. 1.64). This risk increased as the number of previous cesarean sections increased (R.R. 1.53 for one previous section, 2.63 for two or more). The incidence of an anterior placenta previa and placenta accreta was significantly increased in those with previous cesarean scars. The incidence of placenta accreta was 1.18% among patients with placenta previa, 80% being in patients with previous cesarean section. The relative risk for placenta accreta in patients with placenta previa was 35 times higher in those with a previous cesarean section than in those with an unscarred uterus. CONCLUSION: The association of previous cesarean section with placenta previa and placenta previa accreta is confirmed. Patients with an antepartum diagnosis of placenta previa who have had a previous cesarean section should be considered at high risk for developing placenta accreta.
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