Uteroplacental blood flow velocity waveforms in the second and third trimesters of normal pregnancy as related to the placenta location

Abstract The systolic/diastolic ratios ( A B ) of Uteroplacental blood flow velocity wave-forms as related to the placenta location were investigated by continuous-wave Doppler ultrasound in 67 normal pregnancies at 18–21 weeks, in 111 at 31–33 weeks, and in 34 at 40–41 weeks of gestation. Using real-time ultrasound, the placenta was located laterally in 48%, posteriorly in 30% and anteriorly in 22% of the pregnancies. A B values decreased slightly with advancing gestational age. With lateral placenta location, statistically significant higher A B values were found in vessels on the nonplacental side at 31–33 weeks of gestation (2.07 ± 0.43 versus 1.74 ± 0.27; p A B values in the vessels on the placental and nonplacental sides. There were also no differences in A B values between left and right uteroplacental vessels with anterior or posterior placenta locations in any of the gestational age groups.