BEHAVIORAL STATES AND DOPPLER VELOCIMETRY OF THE RENAL-ARTERY IN THE NEAR-TERM HUMAN FETUS

Transition of fetal behavioural state IF to 2F coincides with cardiova scular changes measured by Doppler velocimetry e.g. a decrease in puls atility index (PI) in the internal carotid arteries and in the descend ing aorta, indicating redistribution of blood flow. Recently, we repor ted a considerable reduction in fetal urine production rate of 47% dur ing fetal behavioural state 2F as compared to 1F. It was suggested tha t this reduction is caused by an increase in renal vascular resistance during 2F. Using Doppler ultrasound, flow velocity waveforms (FVW) of fetal renal arteries were recorded during behavioural states 1F and 2 F. Fetal behavioural states 1F and 2F were assessed by recording fetal heart rate pattern, eye movements and body movements. The PI of the r enal artery FVWs were calculated as an index of renal vascular resista nce to blood flow. Fifteen healthy pregnant women between 36 and 40 we eks gestational age were studied and the relationship between fetal re nal vascular resistance to blood flow and behavioural states was deter mined. We found that PI values in the renal arteries did not change re lative to behavioural state 1F and 2F. These findings suggest that ren al vascular resistance to blood flow is not appreciably different in 1 F and 2F. This is in contrast with urine production rate which is almo st reduced by half during 2F in the near term fetus.