Cesarean Scar Ectopic Pregnancy
March 1, 2025
By Vinita Goyal, MD, MPH
Cesarean scar ectopic pregnancy (CSEP) is a complication in which an embryonic pregnancy implants in the fibrous scar of a previous cesarean incision.1 This abnormally located pregnancy places the patient at increased risk for uterine dehiscence, hemorrhage, and abnormal placentation as the pregnancy progresses.
Incidence
The true incidence of CSEP remains uncertain, since this condition likely is underdiagnosed and underreported in clinical practice. The most commonly cited estimates range from one in 1,800 to one in 2,226 pregnancies.1,2 However, these figures come primarily from specialized centers and may not reflect the true population-based incidence.
The challenge in establishing true incidence is further complicated by missed diagnoses. In a review of 751 CSEP cases, 107 (13.6%) initially were misdiagnosed as cervical pregnancies, spontaneous abortions in transit, or low implantation intrauterine pregnancies.2 This suggests that the actual incidence may be higher than currently reported figures.
The reported incidence appears to be increasing over time, which may be attributable to improved imaging capabilities with transvaginal ultrasonography, increased physician awareness of the condition, and, most significantly, the rising global cesarean delivery rates.1,2
Patient Presentation
The clinical presentation of CSEP is highly variable, ranging from asymptomatic at initial detection to uterine rupture with hemoperitoneum and hemodynamic collapse.1,2 In one systematic review of CSEP cases, approximately one-third of patients were asymptomatic with diagnosis made incidentally during routine first-trimester ultrasound.2 Another one-third presented with painless vaginal bleeding, while nearly one-quarter experienced pain with or without bleeding.2
The average gestational duration at diagnosis typically is in the first trimester, with most cases identified between five and eight weeks’ gestation.2,3 However, diagnosis can be delayed into the second trimester, particularly when early ultrasound is not performed or when initial ultrasound assessment fails to recognize the condition.4
Clinicians should maintain a high index of suspicion for CSEP in any patient with a prior cesarean delivery presenting for early pregnancy care.2,5 It is unclear whether the number of previous cesarean deliveries increases the risk of CSEP. Among patients diagnosed with CSEP, 52% had a single previous cesarean delivery.1 While hysterotomy closure technique may be associated with post-cesarean myometrial defects, there are no data on type of closure and CSEP risk.1,5 Previous cesarean delivery for breech presentation may be associated with CSEP, possibly because of a thicker hysterotomy scar leading to poor healing.1,6,7 Other risk factors that should prompt careful evaluation for CSEP include CSEP diagnosis in a previous pregnancy and early pregnancy with placenta previa.6,7
Clinical symptoms warranting urgent evaluation include severe vaginal bleeding (occurring in 12.9% of cases with fetal cardiac activity), lower abdominal pain, and signs of hemodynamic instability.1,8 When CSEP is misdiagnosed as a threatened abortion, miscarriage, or low-lying intrauterine pregnancy, dilation and curettage for presumed failed pregnancy can result in massive hemorrhage and emergency surgical intervention, potentially necessitating hysterectomy.2,9
Sonographic Findings
Transvaginal ultrasound is the primary imaging modality for diagnosing CSEP, offering superior resolution compared to transabdominal approaches.1,2 Ultrasound criteria for CSEP diagnosis include: an empty uterine cavity and endocervix; placenta, gestational sac, or both embedded in the hysterotomy scar; a triangular (at ≤ 8 weeks’ gestation) or rounded or oval (at > 8 weeks’ gestation) gestational sac that fills the scar; a thin (1 mm to 3 mm) or absent myometrial layer between the gestational sac and bladder; a prominent vascular pattern at or in the area of the scar on color Doppler; and an embryonic of fetal pole, yolk sac, or both with or without fetal cardiac activity.1,3 All of these criteria may not be observed.
Additional important sonographic findings include placental lacunae (seen in 78% to 81% of cases after seven weeks), bulging or ballooning of the lower uterine segment, disrupted bladder line interface, and a crossover sign characterized by the gestational sac appearing to cross over the endometrial line, indicating its location within the scar tissue.6,10
The benefit of magnetic resonance imaging (MRI) used as adjunct to ultrasound or over ultrasound alone is unknown. MRI may provide information about the degree of invasion and evidence of placenta accreta spectrum (PAS).1
Two distinct implantation patterns have been identified. Endogenic (on the scar) implantation of the cesarean ectopic refers to a pregnancy growing toward the uterine cavity with measurable myometrial thickness (usually 2 mm to 3 mm) between the gestational sac and bladder. Exogenic (in the niche) implantation refers to CSEP growing toward the bladder or abdominal cavity with minimal (< 2 mm) or no myometrial thickness between the gestation sac and bladder.2,11 The implantation pattern may predict pregnancy outcome; exogenic CSEP is associated with hysterectomy with PAS at the time of cesarean delivery.1,3,9,11
Early accurate diagnosis is crucial but challenging. After seven weeks’ gestation, the gestational sac typically begins moving toward the uterine cavity while the placenta remains anchored at its original implantation site.2,4 This evolution can lead to misdiagnosis as a normal intrauterine pregnancy if attention is not paid to the placental location and vascularity.2 Given the importance of prompt diagnosis, referral to an experienced provider may be preferrable to ongoing follow-up examinations that are likely to delay diagnosis.1
Management
The Society of Maternal-Fetal Medicine (SMFM) advises that CSEP treatment decisions should be guided by the principal goal of preserving maternal health, followed by the secondary goal of preserving fertility when possible.1
The optimal management of CSEP is uncertain and may be based on clinical presentation, gestational duration, myometrial thickness, and available expertise.1,3 Evidence about CSEP management is derived primarily from case series. There are limited randomized trials comparing treatment approaches. Treatment options can be broadly categorized into surgical approaches, medical management, and adjunctive treatments. Interventional approaches are superior to medical management.1
The surgical modalities that have been described for CSEP treatment include hysteroscopy, laparoscopy, laparotomy, open surgery, transvaginal surgery, sharp curettage, needle-guided sac decompression, and uterine aspiration. Medical modalities include methotrexate (both local guided injection and systemic administration) and direct potassium chloride (KCl) injection. Adjunctive treatments include uterine artery emobolization (UAE), high-intensity focused ultrasound imaging, and use of balloon catheters. Clinical evidence also describes using combinations of these methods.1
There is substantial risk for complications with any management approach. The overall complication rate is reported to be 44.1%, including unplanned emergency operations that required hysterectomy (4.8%), laparotomy (5.3%), and UAE (2.9%).1 Treatment modalities with the highest complication rate are intramuscular methotrexate alone (62.1% complication rate), sharp curettage (61.9% complication rate), and UAE (46.9% complication rate).6,10 In addition to a high complication rate, additional treatment is reported to be required after 52% of curettage cases.1 The lowest reported complication rates are with hysteroscopy and intragestational injection of methotrexate or KCl.1
Treatment modalities with the lowest reported success in resolving CSEP include expectant management, curettage, UAE with methotrexate, systemic methotrexate, and local and systemic methotrexate. The highest success rates are with transvaginal CSEP resection (99.2% success, 0.9% complications), laparoscopy (97.1% success, no reported complications), and UAE with curettage and/or hysteroscopy (95.4% success, 1.2% complications).2,3
A newer approach, the use of a double balloon cervical catheter to compress the cervix and CSEP, has a reported 97.7% success and 4.2% complication rate.7 Gravid hysterectomy is the definitive management of CSEP and may be particularly appropriate for patients presenting with CSEP in the second trimester or for those who do not desire future fertility.1
Given the available evidence, SMFM suggests that operative resection (with transvaginal or laparoscopic approaches when possible) or ultrasound-guided uterine aspiration be considered for the surgical management of CSEP, and that sharp curettage alone be avoided. In the case of medical management of CSEP, SMFM suggests the use of intragestational methotrexate (73.9% success with a single dose, 88.5% success with additional doses) with or without other treatment modalities and that systemic methotrexate alone not be used to treat CSEP.1 When patients with CSEP who have been treated medically are observed, the gestational mass can take weeks to months to resolve. During the post-treatment observation period, patients should be monitored for concerning symptoms, such as hemorrhage or uterine arteriovenous malformation (AVM) development.
Current evidence suggests against expectant management in most cases because of the high risks of severe maternal morbidity.2,9 Expectant management is associated with a 50% to 100% hysterectomy rate, usually associated with PAS, and a greater than 50% severe complication rate.12 In cases of recognized CSEP with detected fetal cardiac activity, SMFM does not recommend expectant management because of the high risk of severe maternal morbidity.1
Expectant management of CSEP without fetal cardiac activity has an unpredictable course, often taking several months to resolve spontaneously and is associated with AVM, leading to persistent, severe vaginal bleeding, the need for UAE, or hysterectomy. This approach requires serial ultrasounds, serum beta-human chorionic gonadotropin (hCG) testing, and patient monitoring for bleeding and pelvic pain.1
In patients who choose expectant management and continuation of a CSEP, SMFM recommends repeated cesarean delivery between 34 0/7 and 35 6/7 weeks’ gestation. As with PAS, delivery should occur at level III or level IV facilities with appropriate expertise and resources, which includes the capability to manage massive hemorrhage. A multidisciplinary team approach to delivery is recommended, and the team should be prepared for the potential need for cesarean hysterectomy and massive transfusion.1 Patients whose fertility has been preserved also should be counseled about a 16% to 25% risk for recurrent CSEP in future pregnancies.1
Conclusion
CSEP is associated with a high risk of patient morbidity and mortality. Maintaining a high index of suspicion for CSEP in any pregnant patient with prior cesarean delivery is of critical importance. Few recognized CSEPs continue to viable gestational duration. Expectant management of CSEP is not recommended. Surgical treatment is the most successful approach with the fewest complications.
Vinita Goyal, MD, MPH, is Clinician Researcher, Alamo Women’s Health Clinic of Albuquerque, Albuquerque, NM.
References
1. Society for Maternal-Fetal Medicine (SMFM); Miller R, Gyamfi-Bannerman C; Publications Committee. Society for Maternal-Fetal Medicine Consult Series #63: Cesarean scar ectopic pregnancy. Am J Obstet Gynecol. 2022;227(3):B9-B20.
2. Timor-Tritsch IE, Monteagudo A, Cal G, et al. Cesarean scar pregnancy: Diagnosis and pathogenesis. Obstet Gynecol Clin North Am. 2019;46(4):797-811.
3. Ban Y, Shen J, Wang X, et al. Cesarean scar ectopic pregnancy clinical classification system with recommended surgical strategy. Obstet Gynecol. 2023;141(5):927-936.
4. Premkumar A, Huysman B, Cheng C, et al. Placenta accreta spectrum in the second trimester: A clinical conundrum in procedural abortion care. Am J Obstet Gynecol. 2025;232(1):92-101.
5. Antoine C, Meyer JA, Silverstein J, et al. Endometrium-free closure technique during cesarean delivery for reducing the risk of niche formation and placenta accreta spectrum disorders. Obstet Gynecol. 2025; Jan 9. doi:10.1097/AOG.0000000000005813. [Online ahead of print].
6. Wang Q, Peng HL, He L, Zhao X. Reproductive outcomes after previous cesarean scar pregnancy: Follow up of 189 women. Taiwan J Obstet Gynecol. 2015;54(5):551-553.
7. Grechukhina O, Deshmukh U, Fan L, et al. Cesarean scar pregnancy, incidence, and recurrence: Five-year experience at a single tertiary care referral center. Obstet Gynecol. 2018;132(5):1285-1295.
8. Society for Maternal-Fetal Medicine (SMFM); Miller R, Timor-Tritsch IE, Gyamfi-Bannerman C. Society for Maternal-Fetal Medicine (SMFM) Consult Series #49: Cesarean scar pregnancy. Am J Obstet Gynecol. 2020;222(5):B2-B14.
9. Cal G, Timor-Tritsch IE, Palacios-Jaraquemada J, et al. Outcome of cesarean scar pregnancy managed expectantly: Systematic review and meta-analysis. Ultrasound Obstet Gynecol. 2018;51(2):169-175.
10. Timor-Tritsch IE, Monteagudo A, Santos R, et al. The diagnosis, treatment, and follow-up of cesarean scar pregnancy. Am J Obstet Gynecol. 2012;207(1):44.e1-13.
11. Kaelin Agten A, Cali G, Monteagudo A, et al. The clinical outcome of cesarean scar pregnancies implanted on the scar versus in the niche. Am J Obstet Gynecol. 2017;216(5):510.e1-510.e6.
12. Jurkovic D, Tellum T, Kirk E. Cesarean scar pregnancy IS an ectopic pregnancy. Ultrasound Obstet Gynecol. 2022;59(6):831-832.
Cesarean scar ectopic pregnancy is a complication in which an embryonic pregnancy implants in the fibrous scar of a previous cesarean incision. This abnormally located pregnancy places the patient at increased risk for uterine dehiscence, hemorrhage, and abnormal placentation as the pregnancy progresses.
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