Fetal urine production and micturition and fetal behavioral state

The rate of fetal urine production and the incidence of fetal micturition was compared in periods of fetal sleep and awakeness. Sonography and fetal heart rate monitoring were concomitantly performed on 12 normal term pregnancies. Fetal bladder volumes were serially calculated, and the rate of urine production and micturition were compared between the periods of fetal sleep and awakeness. Fetal micturition occurred almost exclusively during periods of fetal awakeness (p = 0.001). There were no demonstrable differences in the rates of urine production during periods of fetal sleep and awakeness. Fetal micturition is behavioral-state dependent. Nevertheless, the fetal behavioral state is not a necessary consideration when applying urine production measurements as a test of fetal well-being.