Retroperitoneal ectopic pregnancy after in vitro fertilization: A case report of a patient with bilateral salpingectomy.

Retroperitoneal ectopic pregnancy (REP) is a rare obstetric condition caused by the mislocalization of the gestational mass. The unexpected location often results in missed or delayed diagnoses, which can complicate the treatment process. We report the case of a 34-year-old Asian woman who presented to the hospital 31 days after embryo transfer with mild vaginal bleeding. A history of bilateral salpingectomies was established. Two operations were performed before we were able to successfully remove the gestational sac from the retroperitoneal cavity. The histologic finding suggested an interesting migration pathway for the pregnancy. REP should be considered when a visible gestational sac cannot be detected on ultrasound in the expected locations, particularly among patients who undergo treatment using assisted reproductive techniques (ART), and have a history of bilateral salpingectomies. Magnetic resonance imaging (MRI) plays a vital role in diagnosing REP and guiding surgical interventions. A multidisciplinary team is necessary to treat REP, and monitoring beta-human chorionic gonadotropin (βHCG) levels and histologic findings remain essential during follow-up.