Different changes in resistance index between uterine artery and uterine radial artery during early pregnancy.

BACKGROUND

Changes in blood flow impedance of the uterine artery (UA) and uterine radial artery (RA) which is in the lower-extremity of the UA were examined during early pregnancy.

METHODS

Blood flow impedance was assessed by transvaginal color-pulsed-Doppler-ultrasonography in 72 women from weeks 4-16 of pregnancy and expressed as a resistance index (RI).

RESULTS

RA-RI remained at the late-luteal phase level until the 5th week of pregnancy, decreased until the 7th week, and remained low until the 10th week. UA-RI remained at the late-luteal phase level until the 10th week, and then gradually decreased until the 16th week. In nine women with spontaneous abortion, five out of six women with impaired growth of the gestational sac showed high RA-RI at the 6th week of pregnancy, whereas all three women with loss of fetal heart beat at the 8th week showed normal changes in RA-RI.

CONCLUSIONS

Our results show different changes in blood flow impedance between the UA and RA during early pregnancy. A significant decrease of RA-RI after the 5th week may reflect vascular remodeling in the maternal-fetal interface at placentation, whereas a significant decrease of UA-RI after the 10th week may reflect changes of the whole uterine blood flow associated with uterine growth.