Choledochal cysts (CDCs) are increasingly being diagnosed antenatally. The timing of surgery in this group of patients is unclear. We undertook a prospective randomized trial to establish the optimal timing of surgery for prenatally diagnosed asymptomatic CDCs.Between 2003 and 2011, 68 fetuses with ultrasound-detected subhepatic cysts (ie, potential CDC) were randomized into 2 groups: (1) early (≤1 month) operation group (n = 34) and (2) late (>1 month) operation group (LO; n = 34). Operative time, postoperative hospital stay, drainage duration, postoperative complications, and perioperative ultrasonographic and laboratory results were analyzed.During the first month of life, 32 infants became symptomatic (eg, became jaundiced) and were excluded from the trial. This left 36 neonates who were asymptomatic (early operation, n = 16; LO, n = 20) and constituted the study group. It is noteworthy that a further 9 infants in the LO group then became symptomatic after 1 month of age. Grades III and IV hepatic fibroses were significantly more common in the LO group and in patients who were diagnosed during early pregnancy. Interestingly, liver functions in patients diagnosed at early fetal stage were only moderately deranged. Median follow-up period was 36 months. Neither mortality nor complications of bile leak or anastomotic stricture were encountered. However, complete liver function normalization was significantly delayed in the LO group and in patients with high-grade hepatic fibrosis.Prenatally diagnosed CDC is a distinct group with a tendency of developing liver fibrosis immediately after birth. Early surgical intervention is warranted in the neonatal period.