A multi-center study to evaluate the dynamic changes of uterine artery and umbilical artery flow in a normal pregnancy and hypertensive disorders in pregnancy

Abstract

To investigate the dynamic changes of uterine artery and umbilical artery in the first, second, and third trimester of normal pregnancy and hypertensive disorders in pregnancy (HDP). A multi-center prospective study was conducted on 1098 women with normal singleton pregnancies at the first prenatal visit in the Second West China Hospital of Sichuan University, First Affiliated Hospital with Nanjing Medical University, Beijing Obstetrics and Gynecology Hospital Affiliated to Capital Medical University, Wuhan Union Hospital Affiliated to Medical School of Huazhong University of Science and Technology and Renji Hospital Affiliated to Medical School of Shanghai Jiao Tong University from April 2005 to July 2006, with the average age of (28.3 ± 3.3). The pulsatility indices (PI), resistance indices (RI) and systolic to diastolic velocity ratios (S/D) of uterine artery and umbilical artery were measured for all subjects in the first (10th-14th gestational weeks), second (20th-26th gestational weeks) and third trimester (30th-36th gestational weeks), respectively. In this longitudinal study, women who developed HDP were classified into HDP group, and the rest into normal pregnancy group. (1) Among the 1098 pregnant women, 44 developed HDP during the index pregnancy, including 20 gestational hypertension, 15 mild pre-eclampsia and 9 severe pre-eclampsia, giving an incidence of 4.17%, and the rest 1054 were normal until delivery. (2) In the normal pregnancy group, the RI, PI and S/D of uterine artery were decreased with the progress of pregnancy (RI: 0.64, 0.57, 0.50; PI: 1.24, 0.98, 0.80; S/D: 3.26, 2.58, 2.20; P < 0.01). However, the above indices showed an increasing trend with the increase of gestations in the HDP group (RI: 0.55, 0.67, 0.64; PI: 1.22, 1.36, 1.20; S/D: 3.18, 3.41, 3.05; P < 0.01). In the second and third trimester, the RI, PI and S/D of uterine artery in the HDP group were higher than those in the normal pregnancy group (P < 0.01). (3) In the normal pregnancy group, the RI, PI and S/D of the umbilical artery decreased from the second to the third trimester (RI: 0.71 and 0.58; PI: 1.16 and 0.87; S/D: 3.58 and 2.48; P < 0.01). However, no significant difference was found in the RI, PI and S/D value of umbilical artery in the second and third trimester between the normal and HDP group (RI: 0.71 and 0.63; PI: 1.20 and 0.95; S/D: 3.71 and 2.69; P > 0.05, respectively), despite the decreasing trend in the HDP group. In uncomplicated pregnancies, the blood flow resistance of uterine artery decreases and the end-diastolic blood flow of uterine artery increases with the progress of pregnancy. However, in pregnant women with HDP, the blood flow resistance of uterine artery increases significantly with the increase of gestations which shows significant difference to that in normal pregnancies. The blood flow resistance of umbilical artery decreases in both normal and HDP pregnant women with the increasing gestational age.