Urine production rate is related to behavioural states in the near term human fetus

OBJECTIVE: To investigate the relation between hourly fetal urine production rate (HFUPR) and behavioural states 1F and 2F (corresponding to quiet and active sleep, respectively) in normal near term fetuses. DESIGN: An observational study. SETTING: A clinic for antenatal care at a university hospital. SUBJECTS: Nineteen healthy pregnant women examined at 37 to 40 weeks of gestation. MAIN OUTCOME MEASURES: Fetal behavioural states (1F and 2F) were assessed by means of fetal heart rate patterns (FHR A and FHR B). Using real time ultrasonography, HFUPR (ml/h) was estimated during behavioural states 1F and 2F. RESULTS: During behavioural state 1F, HFUPR was significantly higher than during state 2F (P < 0.01). HFUPR falls by 47% from 50.8 +/- 24.4 ml/h in state 1F to 25.7 +/- 15.0 ml/h in state 2F. CONCLUSIONS: During active sleep (state 2F) hourly fetal urine production rate is considerably reduced as compared to quiet sleep (state 1F).