Umbilical velocimetry in normal pregnancy.
Five hundred ninety-six normal pregnancies were evaluated with continuous Doppler to determine the changes in velocimetry between 17 and 42 weeks gestation. The wave-form was identified by its characteristic sharp systolic rise and slow diastolic decay; plotting the S/D ratio as a function of the gestational age reveals a progressive decline in the S/D ratio as gestation progresses. A significant drop occurred around 30 weeks when the mean S/D ratio dropped from 3 (29 weeks) to 2.6 (31 weeks) reflecting decreased placental resistance.
Dor
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Maimonides Hospital Medical Center, Department of Obstetrics and Gynecology, Brooklyn, NY 11219.
Shtern
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M
D001783:Blood Flow Velocity / Q000502:physiology; D005260:Female; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy / Q000502:physiology*; D014465:Ultrasonics; D014463:Ultrasonography; D014469:Umbilical Arteries / Q000502:physiology*