Placenta Extending From the Anterior to the Posterior Uterine Wall: A Rare Case of Pregnancy With a Partial Septate Uterus.

Placental attachment spanning from the anterior to the posterior uterine wall, resulting in the formation of two uterine cavities, presents a diagnostic challenge in obstetrics. Differential diagnoses include placental abruption, multiple gestations, placental variations, and uterine anomalies. Accurate prenatal identification is often difficult, especially when anomalies are not detected during early pregnancy. We report a rare case of a 27-year-old primigravid Japanese woman with a placenta spanning from the anterior to the posterior uterine wall, creating two cavities. At 35 weeks of gestation, ultrasound suggested an unusual placental position, with fetal parts located in separate cavities. At 37 weeks and three days, a cesarean section was performed for breech presentation. Intraoperatively, a partial uterine septum was palpated postplacental removal, with a planar fundus and no retroplacental hematoma. Postoperative ultrasound confirmed the diagnosis of a partial septate uterus. Although septate uterus is the most common uterine anomaly, it often remains undiagnosed in women without infertility. This case highlights the importance of considering uterine anomalies when placental morphology is atypical, especially in the absence of a prior diagnosis, as early recognition is crucial for appropriate perinatal management.