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Updated: Jul 9, 2026

Ultrasonography in Experimental Reproductive Investigations on Rats
Published on: December 2, 2017
Different changes in resistance index between uterine artery and uterine radial artery during early pregnancy
H Tamura1, I Miwa, K Taniguchi
1Department of Obstetrics and Gynecology, Yamaguchi University Graduate School of Medicine, Minamikogushi 1-1-1, Ube 755-8505, Japan.
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.
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