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Umbilical velocimetry in normal pregnancy.
1Maimonides Hospital Medical Center, Department of Obstetrics and Gynecology, Brooklyn, NY 11219.
Summary
Doppler velocimetry in 596 pregnancies shows the systolic/diastolic (S/D) ratio progressively declines with gestational age. This indicates reduced placental resistance, particularly after 30 weeks of gestation.
Area of Science:
- Obstetrics and Gynecology
- Fetal Medicine
- Medical Imaging
Background:
- Doppler velocimetry is crucial for assessing fetal well-being.
- Understanding normal hemodynamic changes throughout pregnancy is essential for identifying potential complications.
Purpose of the Study:
- To establish normative data for Doppler velocimetry in normal pregnancies.
- To characterize the changes in the systolic/diastolic (S/D) ratio between 17 and 42 weeks of gestation.
Main Methods:
- Continuous Doppler ultrasound was used to evaluate 596 normal pregnancies.
- Wave-form analysis focused on systolic rise and diastolic decay.
- The S/D ratio was plotted against gestational age.
Main Results:
- A progressive decline in the S/D ratio was observed as gestation advanced.
- A significant drop in the mean S/D ratio occurred around 30 weeks gestation.
- The mean S/D ratio decreased from 3 at 29 weeks to 2.6 at 31 weeks.
Conclusions:
- The declining S/D ratio reflects decreasing placental vascular resistance.
- These findings provide a reference range for normal Doppler velocimetry in pregnancy.
- Changes in placental resistance are a key factor in fetal development and well-being.