Intrauterine Pregnancy in a Uterus Didelphys Mimicking an Ectopic Pregnancy.

Uterus didelphys is a rare congenital uterine anomaly resulting from the complete failure of fusion of the Müllerian ducts. Early pregnancy in a duplicated uterus can present a significant diagnostic challenge, as the gravid lateralized hemi uterus may be mistaken for an adnexal mass. A 31-year-old woman presented at six weeks of gestation with mild abdominal cramping. A two-dimensional transvaginal ultrasound revealed an empty main uterine cavity and a gestational sac adjacent to the right ovary. Given a serum beta-hCG level of 4,200 mIU/mL and concern for an ectopic pregnancy, urgent diagnostic laparoscopy was performed. Surgery revealed a completely duplicated uterus, with the pregnancy confirmed to be intrauterine within the right hemi-uterus. A subsequent three-dimensional transvaginal ultrasound confirmed the diagnosis of uterus didelphys. The pregnancy progressed without complications, resulting in a planned cesarean delivery at 39 weeks due to breech presentation. Uterus didelphys can closely mimic an ectopic gestation during early ultrasound assessment. Early integration of three-dimensional transvaginal ultrasound in stable patients with suspected ectopic pregnancies is an invaluable tool to accurately identify congenital anomalies and prevent unnecessary surgical interventions.