Antenatal diagnosis of a third trimester interstitial pregnancy: a case report.

Interstitial pregnancy cases that advance to term, or near term, are occasionally reported. We present an unusual case of a third trimester interstitial pregnancy with antenatal diagnosis and expectant management. She presented at 20 weeks of pregnancy with an early preterm premature rupture of membranes, and expectant management was initiated. The ultrasound suggested an interstitial location and a posterior magnetic resonance image, obtained at 26 weeks, confirmed the diagnosis. Because of the risk of uterine rupture, an elective cesarean section was performed at 28 weeks. During the laparotomy, the uterine fundus appeared intact with an asymmetric bulge that provided evidence of placenta increta. The baby was delivered, and an obstetric hysterectomy was performed. The newborn was admitted to the neonatal intensive care unit with a severe respiratory distress syndrome. No response to mechanical ventilation was observed, and neonatal death was reported. A uterine pathological examination confirmed the diagnosis.