Urine production and bladder function in fetuses with open spina bifida.

Hourly fetal urine production rate (HFUPR) and bladder filling and voiding were determined by real-time ultrasonography in 13 fetuses with open spina bifida (OSB) and compared with those of 101 normal fetuses from uncomplicated pregnancies at 16-40 weeks gestation. In normal pregnancy, the fetal bladder volume increases linearly with time and then decreases rapidly with micturition. The mean cycle length does not change significantly with gestation but both the mean bladder volume and HFUPR increase. In fetuses with OSB, ultrasonographic examination has demonstrated deviations from normal in both bladder filling and bladder emptying.