ObjectiveTo examine whether maternal meal ingestion affects the fetal circulation in uncomplicated pregnancies.MethodsA simple crossover blinded study was designed for late uncomplicated singleton pregnancies. After overnight fasting, two different maternal meal states were tested. In one state, pregnant women had a standard 600-kcal breakfast at 8 AM (phase A). The other state consisted of maintaining fasting (phase B). Both states were assigned to each woman within 3 days in randomized order. Fetal Doppler studies of the umbilical, middle cerebral, and renal arteries and the descending aorta were performed at 7 AM (the fasting state) and at 10 AM (the fed state or the continuous fasting state).ResultsTwenty women underwent the crossover study. Regardless of the maternal meal state, no significant change was observed in the pulsatility index (PI) of either the umbilical artery (n= 20), the middle cerebral artery (n= 19), or the descending aorta (n= 15). However, the PI of the fetal renal artery decreased significantly after maternal meal ingestion (n= 14) (phase A, 2.36 ± 0.16 versus 2.09 ± 0.33;P= .021). There was no such change in the PI after prolonged fasting (phase B, 2.44 ± 0.32 versus 2.39 ± 0.44;P= .75).ConclusionFetal renal artery resistance decreased after maternal meal ingestion in normally grown fetuses during late pregnancy. This decrease in the resistance may be associated with increased fetal urine production after maternal meals.