Caution in antenatal intervention.

We assessed 18 fetuses who harbored a urinary tract malformation that was diagnosed by antenatal sonography. The antenatal diagnosis corresponded to the postnatal diagnosis in 66 per cent of the cases. We review the course of 6 fetuses who had catheters placed percutaneously to drain dilated urinary tracts that were believed to be caused by posterior urethral valves (5) or an obstructed megaureter (1). Only 2 of these fetuses exhibited valves postnatally. No fetus had any recognized benefit from the antenatal intervention. We found that sonography may not readily differentiate fetuses with hydronephrosis with obstruction from those without obstruction. From this experience we conclude that intervention in pregnancies suspected of harboring a fetus with a malformed urinary tract should be done cautiously. Antenatal sonography is useful to identify the fetus with a dilated urinary tract. This identification permits perinatal specialists to be alerted so that preparations for reconstructive surgery in such cases can be made early postpartum.