Influence of short-term indomethacin therapy on fetal urine output.

Eight pregnancies ranging from 27-32 weeks' gestation were treated for preterm labor with oral indomethacin. The dosage regimen was 25 mg every four hours in four patients and 25 mg every six hours in the other four patients. The maximum duration of indomethacin therapy was 72 hours. In three patients, fetal ductus arteriosus constriction mandated discontinuation of indomethacin at 24 hours. Sonographic assessment of hourly fetal urine output was performed before therapy, at multiple regular intervals during therapy, and 24 hours after the last dose of indomethacin. A dramatic decline was noted from the mean baseline fetal urine output of 11.2 mL/hour. The mean fetal urine output at five, 12, and 24 hours during therapy was 2.2, 1.8, and 1.8 mL/hour, respectively (P less than .05). Twenty-four hours after completion of indomethacin therapy, the mean fetal urine output was 13.5 mL/hour. Poor correlation (r = 0.14, P less than .05) was noted between maternal serum indomethacin levels and hourly fetal urine output. This significant decline in urine output is consistent with other results in neonatal and adult animals and humans. Furthermore, it implies a role for prostaglandins in controlling urine output during fetal life.