FLOW PARAMETERS OF THE NORMAL ARTERIAL DUCT IN THE FETUS

The increasing interest in arterial duct flow patterns in the fetus wa rrants the establishment of an accurate range of normal flow parameter s throughout gestation. We therefore undertook a prospective echocardi ographic study of 181 normal fetuses from the 16th to the 40th week of gestation. Adequate Doppler interrogation of the duct was obtained in 71% of the fetuses examined. Peak gradient, mean gradient and flow ve locity integral in systole and diastole were digitized. The peak systo lic gradient throughout pregnancy measured 2.7+/-1.4 mmHg with a sligh t tendency to increase with gestational age (r=0.58). The peak ratio, defined as peak systolic gradient divided by peak diastolic gradient ( 28.1+/-14.9), did not vary significantly with gestational age. This ti me-independent index complements peak systolic flow in the assessment of normal and abnormal ductal flow. The definition of the normal range for ductal flow parameters, based on this relatively large fetal popu lation, should facilitate the accurate diagnosis of fetal duct constri ction.