Prenatal Diagnosis and Obstetrical Challenges of a Massive Fetal Ascites Affecting One Fetus in a Dichorionic Diamniotic Twin Pregnancy: A Case Report.

Fetal ascites is a rare prenatal condition; it may result from a wide range of underlying etiologies, including structural anomalies, genetic disorders, congenital infections, and metabolic diseases. Despite considerable advances in prenatal investigations, etiology remains unidentified in some cases. Massive fetal ascites may also complicate obstetric management by distorting fetal biometric measurements and influencing delivery planning. We report the case of a 34-year-old woman with a spontaneously conceived dichorionic diamniotic twin pregnancy. At 24 weeks of gestation, massive fetal ascites associated with bilateral hydrocele was diagnosed in a male twin. Maternal infectious investigations were negative except for low-titer Epstein-Barr virus (EBV) IgG positivity. The patient presented with threatened preterm labor at 30 weeks of gestation. Ultrasound estimated the affected fetus to weigh approximately 3.3 kg because of marked abdominal distension secondary to ascites, whereas the actual birth weight was 2.2 kg. The infant died approximately one hour after birth, while the co-twin survived following admission to the neonatal intensive care unit. This case illustrates the diagnostic challenges posed by massive fetal ascites, even after comprehensive prenatal evaluation. It also highlights its obstetrical implications, particularly the impact on fetal weight estimation and perinatal management in twin pregnancies.