Doppler evaluation of umbilical venous and arterial blood flow in the second and third trimesters of normal pregnancy.

Abstract

Duplex Doppler ultrasound was used to measure umbilical venous blood flow in 209 normal pregnant women between 20-40 weeks' gestation. The relationship between umbilical venous blood flow and gestational age increased with gestational age, and is described by the equation y = -187.02 + 12.7x. The relationship between flow per kilogram fetal weight and gestational age (y = 198.629 - 2.24x) yielded values of 153 mL/minute/kg at 20 weeks, 131 mL/minute/kg at 30 weeks, and 108 mL/minute/kg at 40 weeks. Doppler ultrasound was also used to evaluate umbilical arterial waveforms (systolic/diastolic ratio) in 171 normal pregnant women between 20-40 weeks. The relationship between systolic/diastolic ratios and gestational age (y = 6.46 - 0.12x) decreased with advancing gestational age, yielding mean systolic/diastolic ratios (+/- 2 SD) of 4.1 (5.6, 2.6) at 20 weeks, 3.6 (5.1, 2.1) at 24 weeks, 3.1 (4.6, 1.6) at 28 weeks, 2.6 (4.1, 1.1) at 32 weeks, 2.1 (3.6, 0.6) at 36 weeks, and 1.7 (3.1, 0.1) at 40 weeks.