Unicornuate uterus with a non-communicating rudimentary horn discovered during cesarean delivery: a case report.

INTRODUCTION AND IMPORTANCE: Unicornuate uterus is a rare Müllerian duct anomaly resulting from the incomplete development of one Müllerian duct and accounts for approximately 10% of all congenital uterine malformations. It is frequently associated with a rudimentary horn, most commonly non-communicating, and is linked to adverse reproductive outcomes, including miscarriage, preterm birth, malpresentation, and the risk of rudimentary horn pregnancy with potential uterine rupture. CASE PRESENTATION: A 31-year-old primigravida presented at 32 weeks of gestation with preterm labor. She had no history of infertility, miscarriage, or gynecologic complaints and had conceived spontaneously. Ultrasound revealed a breech fetus without additional abnormalities. An emergent cesarean section was performed, resulting in the delivery of a healthy male infant. Intraoperative inspection revealed a left non-communicating rudimentary horn and a unicornuate uterus, classified as American Society for Reproductive Medicine subtype A1b. Postoperative imaging confirmed the diagnosis, and no major urinary tract anomalies were identified, aside from mild bilateral hydronephrosis. The postoperative course was uneventful. CLINICAL DISCUSSION: This case demonstrates that a unicornuate uterus may remain undiagnosed until pregnancy or surgery, as routine ultrasonography may fail to detect non-communicating rudimentary horns. Despite the association with adverse outcomes such as preterm labor and malpresentation - both present in this case - normal reproductive performance is still possible. Intraoperative recognition of Müllerian anomalies is essential for accurate diagnosis, appropriate counseling, and planning of future obstetric care. CONCLUSION: A unicornuate uterus with a non-communicating rudimentary horn does not preclude successful pregnancy outcomes. Vigilant intraoperative assessment during cesarean delivery is crucial for identifying previously unrecognized uterine anomalies, enabling informed counseling and optimized management in subsequent pregnancies.