Prune belly syndrome is a rare disorder characterized by the absence of anterior abdominal wall muscles, bilateral cryptorchidism, and urinary tract malformations. The aim of this case study was to illustrate the developmental sequelae of prune belly syndrome, acquired through a series of antenatal sonography. A 20-year-old woman visited a diagnostic medical sonography center for an obstetrical sonogram. Her fetus was diagnosed with megacystis at 15 weeks’ gestation. The mother returned for repeated appointment and to observe fetal changes during the development of prune belly syndrome. First, the megacystis, hydroureter, and hydronephrosis were noted followed by hazy ascitic and amniotic fluid. The hemodynamics were altered in the umbilical artery, middle cerebral artery, and ductus venosus. Subsequently, the pressure was neutralized, but it was observed after birth that the newborn had cryptorchidism, a distended abdomen with wrinkled wall, and absent right kidney. In conclusion, prune belly syndrome could be caused by megacystis due to bladder outlet obstruction in otherwise normal karyotype fetuses. Megacystis leads to hydroureter, hydronephrosis, and abdominal distention. The persistent abdominal distention gives rise to the underdevelopment of anterior abdominal wall muscles and cryptorchidism.