Sequential changes in uterine artery blood flow pattern between the first and second trimesters of gestation in relation to pregnancy outcome.

OBJECTIVE

To describe sequential changes in uterine artery waveform between the first and second trimesters of gestation and to analyze their association with the subsequent risk of hypertensive disorders and fetal growth restriction (IUGR).

METHODS

Sequential uterine artery Doppler recordings were obtained in a final cohort of 870 singleton pregnancies over two gestational age intervals: 11-14 weeks and 19-22 weeks. The left and right uterine arteries were examined by color and pulsed Doppler and the mean pulsatility index (PI) as well as the presence of a bilateral protodiastolic notch were recorded during both intervals. Pregnancies were followed for occurrence of hypertensive disorders and IUGR.

RESULTS

Mean uterine artery PI showed a significant linear decrease within each of the two intervals considered, while the prevalence of a bilateral notch showed decreasing values only throughout 11-14 weeks of gestation. Sixty-four (7.3%) pregnancies developed a hypertensive disorder and/or IUGR, including three (0.34%) cases of gestational hypertension, 24 cases of pre-eclampsia (2.75%) and 37 (4.25%) of IUGR. Compared with pregnancies with a normal outcome, complicated pregnancies showed a significantly higher prevalence of a bilateral notch and a higher mean PI in each of the two intervals studied. Compared with normal pregnancies, complicated pregnancies had a significantly higher persistence of a bilateral notch (30% vs. 8%), a higher proportion of women with an abnormal first-trimester uterine artery PI shifting to normal in the second trimester (14% vs. 4%) and a higher incidence of a normal first-trimester mean PI that shifted to abnormal in the second trimester (13% vs. 4%). Persistence of an abnormal mean PI from the first to the second trimester identified the group with the greatest risk for adverse perinatal outcome (OR, 10.7; 95% CI, 3.7-30.9). In addition, women in whom the uterine artery mean PI shifted from abnormal to normal between the two trimesters and women in whom the reverse shift occurred showed a similar intermediate risk (OR, 5; 95% CI, 2.1-10.6), comparable to that in women with persistence of a bilateral notch (OR, 5.6; 95% CI, 2.9-10.7).

CONCLUSIONS

The sequence of changes in uterine flow between the first and second trimesters correlates with the subsequent development of hypertensive disorders and IUGR. Women with a persistent abnormal mean PI represent the group with the greatest risk for adverse perinatal outcome.