Abstract
Polyhydramnios is a condition defined as an increase of amniotic fluid volume. Common causes include maternal diabetes, multiple pregnancies, and congenital anomalies. Congenital type C esophageal atresia is one of the causes and often presents with a visible stomach, making prenatal diagnosis difficult. A 37-year-old woman with monochorionic diamniotic twin pregnancy was hospitalized for threatened preterm labor at 26 weeks of gestation. She was also diagnosed with gestational diabetes mellitus and her glucose levels were consistently high during pregnancy despite the initiation of insulin therapy. After admission to hospital, the amniotic fluid volume of the leading twin remained at the lower limit of the normal range, while polyhydramnios appeared in the following twin. Persistent amniotic fluid discordance raised concern for a possible evolving intertwin transfusion process, although the diagnostic criteria for twin-to-twin transfusion syndrome were not met. An emergency cesarean section was performed at 28 weeks due to onset of labor. After birth, twin B showed mild cardiomegaly and polycythemia, findings compatible with recipient-like pathophysiology. Furthermore, the same twin showed a coiled nasogastric tube on chest X-ray and was diagnosed with type C esophageal atresia postnatally. This case illustrates polyhydramnios in the setting of overlapping etiologies, gestational diabetes mellitus, esophageal atresia, and twin amniotic fluid discordance suggestive of an evolving intertwin transfusion process. Clinicians should consider multifactorial causes when managing unexplained polyhydramnios and perform comprehensive fetal evaluations.