Relationship of estradiol and progesterone levels to uterine blood flow during early pregnancy.

The purpose of this study was to examine the relationship of uterine blood flow to serum estradiol and progesterone during early pregnancy. Recumbent uterine artery average velocity, diameter, blood flow volume and uterine and spiral artery resistance were measured using vaginal Doppler ultrasound 118 times in 43 patients during gestational (postmenstrual) weeks 5 to 16. Relationships to serum progesterone and estrogen were analyzed before and after week 10, when intervillous circulation begins, by multiple linear regression analysis and analysis of covariance (ANCOVA) to correct for the effect of gestational age. After correction for gestational age, estradiol was negatively related to uterine artery flow volume (p < 0.05), diameter (p < 0.05), pulsatility index (p < 0.05) and resistance index (p < 0.01) for weeks 5-16 and to diameter (p < 0.05) after week 9. Progesterone was positively related to volume (p < 0.05) and velocity (p < 0.01) for weeks 5-16 and to volume (p < 0.05) for weeks 5 to 9. Spiral artery indices of resistance were unrelated to hormone levels. These results indicate that before the 10th gestational week, uterine blood flow volume is related to progesterone, but not estradiol levels, and suggest that high estradiol levels during and after the 10th week may be associated with decreased uterine blood flow volume.