Rudimentary horn could be a rare congenital uterine anomalies result from incomplete fusion of the two Müllerian ducts throughout embryo-genesis. Pregnancy in an exceedingly rudimentary horn is rare and typically terminates in rupture throughout the late of first or second trimester of pregnancy. We tend to present a rare case of a gravida within the trimester (31 weeks) presented with complain of abdominal pain, nausea, and vomit for 3 days. On presentation, the patient was pale and irritable. Ultrasound scan showed fetus at (30 weeks) with cardiac activity. Cardiotocography reactive. Incision showed horned uterus with pregnancy in rudimentary left horn that was ruptured. Alive fetus was delivered. The rudimentary left horn was excised. The patient was advised to not get pregnant for 3 years. Within one year, the patient came to hospital in active labor at (37 weeks). This case emphasizes the importance of fine antepartum care to avoid morbidity and mortality.