Changes in Placental Blood Flow in the Normal Human Fetus with Gestational Age

Abstract

ABSTRACT. We assessed fetoplacental blood volume flow human fetuses using pulsed-wave Doppler. Our aims were 3-and placental resistance prospectively with Doppler sonog-fold: I ) to quantitate the changes in placental blood volume flow raphy in 74 normal human fetuses of 19 to 42 wk gestation with gestational age and fetal body weight, 2) to determine to determine the changes in placental perfusion with ges-whether placental blood volume flow falls in postdate fetuses tational age. Placental blood volume flow was assessed (greater than 40 wk), and 3 ) to examine the relation between from the umbilical vein as the product of the mean flow umbilical arterial velocity ratio and placental blood volume flow. velocity integral and the cross-sectional area of the umbilical vein. Placental resistance was assessed as the ratio of MATERIALS AND METHODS maximum systolic and minimum diastolic blood flow velocities from an umbilical artery. Umbilical vein blood volumeWe studied 74 normal human fetuses ranging in age from 19 flow increased exponentially ( r = 0.86) with gestational to 42 wk, whose mothers were referred for routine obstetric age from 19 wk to term, and did not decrease in postdate ultrasound examination to assess fetal gestational age and/or fetuses. Umbilical vein blood volume flow increased lin-placental location. Mothers with diabetes, hypertension, preearly with fetal weight ( r = 0.77), although volume flow eclampsia, rhesus-incompatibility, multiple gestations, and preper unit body weight changed little with gestational age. vious fetuses with congenital malformations were excluded. HuUmbilical artery velocity ratio decreased progressively, man fetuses were only included in this study if their biophysical indicating diminishing placental resistance with gestational profiles were normal for their gestational age and any congenital age, but did not correlate closely with umbilical vein blood abnormalities involving the cardiovascular system or any other volume flow. We submit that fetoplacental blood volume organ system were excluded. Each human fetus was studied only flow can be readily calculated directly from the umbilical once to minimize any potential hazard from the Doppler ultravein with Doppler ultrasound and may provide a better sound. Written informed consent was obtained from each index of placental perfusion than the umbilical artery mother, and the protocol was approved by the Brigham and velocity ratio. (Pediatr Res 28: 383-387, 1990) Women's Hospital Human Subjects Committee. Two-dimensional imaging and pulsed-wave Doppler flow studies were performed using a model 77020 AC/AR ultrasonoscope (Hewlett Packard Co., Palo Alto, CA) with either a 3.5-mHz or, more frequently, a 5.0-mHz transducer. Normal fetal growth and viability depend directly upon the The transducer was placed on the maternal abdomen after the fetoplacental circulation for the supply of nutrients, gas, and mother had rested semi-recumbent for 15 min, and each fetus metabolite exchange. Impaired placental blood flow has been was...

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