[Effect of fetal behavioral reactions and respiratory movements on the blood flow in the ductus arteriosus].

Relationship between blood flow velocity waveform and fetal behavioral states was studied in 16 normal pregnancies at 37 to 38 weeks' gestation. The peak flow velocity has demonstrated a statistically significant reduction during active sleep, as against that in quite sleep. These data reflect reduced ductal flow and suggest a redistribution in the left-ventricular and right-ventricular output in favor of the left side of the heart during active sleep. In a prospective cross-sectional study of 49 pregnancies (50 fetuses) between 25th and 38th weeks an exponential increase in breathing-related ductal blood flow velocity modulation was observed with advancing gestational age, reflecting the developing pulmonary vascular bed. Fetal ductal flow velocity waveforms were also recorded in 13 cases of prolonged severe oligohydramnios after membrane rupture before 28 weeks' gestation. Normal ductal blood flow velocity modulation values were associated with normal neonatal lung performance, whereas reduced blood flow velocity modulation values were associated with pulmonary hypoplasia. Fetal breathing-related ductal flow velocity modulation appears to be a promising predictor of neonatal lung performance.