Abstract
A rudimentary horn is a type of congenital uterine anomaly associated with a unicornuate uterus. Rudimentary horn pregnancies (RHPs) are extremely rare and the majority of cases result in second trimester rupture necessitating emergent laparotomy with associated high maternal morbidity and delivery of a previable fetus. We report the case of a 33-year-old G5P0131 female who presented at 15 weeks and 4 days gestational age with pelvic and back pain and imaging favoring an abdominal pregnancy. The patient underwent an exploratory laparotomy with left salpingectomy and excision of an unruptured extrauterine pregnancy that was confirmed to be an RHP on pathologic examination. Postsurgery review of the imaging demonstrated several features consistent with the diagnosis of an RHP that were not initially identified. Furthermore, the patient's medical and surgical histories were notable for several risk factors associated with congenital uterine anomalies that should have heightened the clinical suspicion for an RHP. This case emphasizes how increased familiarity with the risk factors and imaging findings associated with rudimentary horns and RHPs may lead to an earlier and more accurate diagnosis, more timely and appropriate treatment, and ultimately a reduction in maternal and fetal morbidity and mortality.