Uterine artery hemodynamic adaptations through the menstrual cycle into early pregnancy

To estimate the time course of human uterine artery vascular adaptation through the menstrual cycle into early pregnancy.

We prospectively measured the uterine artery pulsatility index, peak systolic velocity, and volumetric blood flow during the menstrual cycle and at 4, 6, and 12 weeks of pregnancy in women who conceived. Upper extremity radial artery hemodynamic changes were examined as a control vessel. Ten subjects conceived within 12 months of menstrual cycle studies. Analyses were performed using repeated measures analysis of variance with P <.05 accepted for significance.

In women who conceived, uterine artery peak systolic velocity demonstrated a significant increase during the period of observation, which began after cycle day 10 (0.36 x 0.02 meters per second) of the menstrual cycle and continued though 12 menstrual weeks (1.05 +/- 0.10 meters per second, P <.001). Uterine artery pulsatility index decreased significantly during the observation window from 3.0 +/- 0.2 in the follicular phase to 1.6 +/- 0.2 at 12 menstrual weeks (P <.001). Blood flow in the uterine artery increased significantly from cycle day 10 (22.2 +/- 1.8 mL per minute) to 12 menstrual weeks' gestation (150.2 +/- 40.3 mL per minute, P <.001). These patterns were significantly different from the patterns observed for the radial artery.

Uterine artery hemodynamic adaptation in early pregnancy follows a continuum established during the menstrual cycle. These adaptations result in decreased uterine artery impedance and increased blood flow. These changes differ from those observed in the upper extremity radial artery (control vessel) suggesting independence of regional pelvic and systemic hemodynamic adaptations.