A large meconium pseudocyst that developed into the generalized type during the antepartum period.

A fetal intraabdominal cystic mass, measuring 6 cm, was detected at 30 weeks of gestation in a 27-year-old gravida 2 para 1 woman. At 33 weeks of gestation, the cyst disappeared. Ultrasonography showed fetal bowel dilatation, polyhydramnios, and intraabdominal calcifications. Fetal meconium peritonitis was diagnosed prenatally. Because the fetal ileus became worse, a cesarean section was performed at 35 weeks of gestation; a female infant weighing 2,131 g with an Apgar score of 8 was delivered. Six hours after birth, the neonate received an ileostomy. The bowel was reanastomosed 42 days after the initial operation. On postoperative pathology, a meconium pseudocyst was diagnosed. To our knowledge, this is the first report of a large fetal meconium pseudocyst that developed into the generalized type in the uterus during the preterm antepartum period.