Placental microvascular changes in twin pregnancies with abnormal umbilical artery waveforms.

Objective: To determine whether there is a relationship between umbilical artery Doppler waveforms and placental histology in twin pregnancies. Methods: The placental vasculature was examined histologically in 01 cases of twin pregnancy in women who had undergone antenatal Doppler umbilical artery waveform analysis. Results: Those fetuses with abnormal systolic-diastolic ratios (S/Ds) showed a reduction in the placental tertiary stem villi arterial vessels compared with fetuses with normal S/Ds. The mean count of small arterial vessels (diameter less than 90 μ) in the placentas from cases with normal S/Ds (below the 95th percentile) was 5.6, whereas the mean arterial count for those with high S/Ds (above the 99th percentile) was 3.9 (P =.039)