Why the study?
How do impedance, mean velocity, and volume of flow in the uterine artery change during normal pregnancy?
How do impedance, mean velocity, and volume of flow in the uterine artery change during normal pregnancy?
Uterine artery impedance decreases while blood velocity and volume flow increase with gestation, with more pronounced changes in the placental uterine artery.
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Provides normative uterine artery Doppler values in pregnancy; leaves open predictive value for complications in prospective cohorts.
In a cross-sectional study of 215 healthy women with singleton pregnancies at 18-42 weeks' gestation, color Doppler imaging was used to identify the main uterine arteries for subsequent pulsed Doppler studies. Flow velocity waveforms were obtained and indices of impedance, mean blood velocity and vessel diameter were measured, and the total volume of blood flow to the uterus was calculated. Impedance to flow decreased, I whereas blood velocity and volume flow increased significantly with gestation. Furthermore, impedance to flow was lower and velocity higher in the placental uterine artery, i.e. closest to the main bulk of the placenta, than in the non-placental artery.
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Bower et al. (1992) studied this question.
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