Cesarean Scar Ectopic Pregnancies: Etiology, Diagnosis, and Management.

Abstract


OBJECTIVE:

To clarify the appropriate way to diagnose and treat an ectopic pregnancy in the uterine scar of a prior cesarean delivery.

DATA SOURCES:

Articles written in English that were published from January 1966 to August 2005 and quoted in the computerized database MEDLINE/PubMed retrieved by using the words “cesarean section,” “cesarean delivery,” “cesarean section scar pregnancy,” and “ectopic pregnancy.” Additional articles were obtained from reference lists of pertinent case reports and reviews.

METHODS OF STUDY SELECTION:

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. Endovaginal ultrasonography was the diagnostic method in most cases, with a sensitivity of 84.6% (95% confidence interval 0.763–0.905). 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.

Introduction

Pregnancy in the scar from a cesarean delivery is located outside the uterine cavity and is completely surrounded by myometrium and fibrous tissue of the scar in the prior low uterine segment. The recognized long-term risks of cesarean delivery are subsequent ectopic pregnancies, uterine rupture, and placental disorders in future pregnancies such as abruptio placentae, placenta previa, and placenta accreta, which is the most serious condition. However, endometrial and myometrial disruption and scarring subsequent to cesarean delivery also may predispose to implantation in the uterine scar, which is even more dangerous than placenta accreta. Invasion of the myometrium early in the first trimester may lead to uterine rupture and profuse bleeding as the pregnancy advances.

There is minimal awareness of the possibility of gestation in a previous cesarean scar, which is often misdiagnosed as a cervical or aborting pregnancy. Because suspicion is low, diagnosis of an early pregnancy in a prior cesarean scar may be delayed, and potentially catastrophic complications may ensue.

We recently encountered a case of a pregnancy in a cesarean scar, which triggered a thorough search of the medical literature to ascertain the most effective approach to this form of ectopic pregnancy. Because we were impressed with the exponential increase in the number of cases reported over the last 5 years, we proceeded with a systematic review of the topic. This article outlines the etiology and the predisposing risk factors and updates our knowledge of available treatments for this life-threatening condition.

CONCLUSION

Pregnancy in cesarean delivery uterine scar in the first trimester has been encountered more commonly over the last decade, and uterine scar may no longer be the most infrequent site for ectopic implantation. This increase in incidence may be attributed to the liberal use of endovaginal ultrasonography in the first trimester and to the worldwide increase in the number of cesarean deliveries. Endometrial and myometrial disruption and scarring caused by the cesarean incision are the main predisposing factors. From our review, it seems that the number of cesarean deliveries does not play a role, inasmuch as more than half (52%) of the reported cases had only one operation. A poorly developed low uterine segment at the time of the cesarean delivery, such as in breech presentation, may predispose to incomplete healing of the scar and to a subsequent implantation of pregnancy in it. In fact, breech presentation was the most common (31.4%) indication for cesarean delivery in the cases we reviewed.

Surprisingly, pain as a presenting symptom was not as frequent as expected, because one third of the patients who were included in this review were completely asymptomatic, and approximately 40% had only painless vaginal bleeding. Sonography was the method used for diagnosis in these patients to ascertain localization and size of the conceptus and its viability. Performed in the first few weeks of conception, endovaginal ultrasonography, with a sensitivity of 84.6%, has dramatically reduced maternal morbidity, enabling medical management in an increasing number of cases. Both 3-dimentional Doppler sonography and magnetic resonance imaging are adjunctive methods in management and follow-up. The rarity of this condition explains the absence of universal guidelines for management. Although several interventions have been used to maintain uterine integrity, none has been universally accepted or found completely reliable.

In more than half of the reported cases, complications occurred, ranging from bleeding to uterine rupture that frequently necessitated additional therapy or hysterectomy. It seems that expectant management is not justified because rupture of the scar and hemorrhage may occur even in the first trimester. Wedge resection of the gestation in the scar and repair of the defect via laparotomy or laparoscopy emerges as a safe therapy, particularly in advanced pregnancies with [beta]-hCG levels exceeding 15,000 milli-International Units/mL. Laparoscopic approach seems reasonable as long as the appropriate expertise and facilities are available should rupture or massive bleeding occur.

Dilation and curettage was complicated by severe hemorrhage in 76.1% of the patients and hysterectomy in 14.2 % of them and, therefore, should not be a first-line therapeutic option. Systemic methotrexate may be effective for patients with [beta]-hCG levels lower than 5,000 milli-International Units/mL. For levels exceeding 5,000 milli-International Units/mL, its simultaneous employment with direct intragestational injection of methotrexate was effective in all 5 cases reported. The above technique may be combined with potassium chloride injection used as an embryocide or with uterine artery embolization to minimize hemorrhage. There are several disadvantages to these conservative treatments: slow decline in [beta]-hCG levels, possible massive bleeding or uterine rupture, and risk for future recurrent implantation.

Patients with history of a pregnancy in a cesarean delivery scar should be advised of the risk for future rupture of the pregnant uterus. Uterine rupture and placenta accreta are serious complications that may occur even if the initial treatment was successful. In general, the risk of uterine rupture in women with prior cesarean is 17-fold higher than in the absence of a uterine scar (0.3–1.7%). However, after a cesarean scar pregnancy, this risk is even higher because of thinning of the scar. Susceptibility to rupture and its timing are unpredictable. Maymon et al recommended preconceptional sonohysterography in women with prior cesarean scar gestation to detect any defect in the scar. Others recommended repair of the scar before any attempt at subsequent conception or at least the use of contraception for 1–2 years. The next pregnancy should be delivered by cesarean before the onset of labor because elasticity of the scar cannot adapt to rapid uterine enlargement in late third trimester. Careful survey for placenta accreta has also been advocated. If present, a cesarean hysterectomy at 32–34 weeks is recommended.

In summary, we reviewed all published case series and case reports on pregnancy in the uterine scar of a prior cesarean delivery. This review is limited because it relies on experience from anecdotal cases. We are aware of the fact that treatment policies should not be based on such reports. However, this review is important because it provides a summary of the different therapeutic modalities, treatment failures, and possible complications. Considering the rarity of pregnancy in a cesarean delivery scar, it would be of great importance to report even individual cases, particularly those with treatment failures or complications, so that eventually universal treatment guidelines can be established.