Patterns of Change in Uterine Artery Doppler Studies Between 20 and 24 Weeks of Gestation and Pregnancy Outcomes

OBJECTIVES: To describe changes in mean uterine artery resistance index and bilateral notches between 20 and 24 weeks of gestation in healthy nulliparous women and to relate these changes to pregnancy outcome. METHODS: A total of 2,189 nulliparous participants in the Screening for Pregnancy Endpoints study had pregnancy outcomes compared between four uterine artery Doppler groups: normal at 20 and 24 weeks of gestation (group 1), normal at 20 weeks and abnormal at 24 weeks (group 2), abnormal at 20 weeks and normal at 24 weeks (group 3), and abnormal at both 20 and 24 weeks (group 4). Abnormal uterine Doppler was defined as 1) mean resistance index greater than the 90th centile; 2) bilateral notches; and 3) a combination of 1, 2, or both. The main outcomes were preeclampsia and small for gestational age (SGA) neonates (less than the 10th customized centile). RESULTS: Preeclampsia developed in 116 (5.3%) women, and 223 (10.2%) delivered SGA neonates. With abnormal Doppler defined as mean resistance index greater than the 90th centile, the rate of SGA increased across Doppler group 1, 156 (8.4%); group 2, 13 (11%); group 3, 25 (19.5%); and group 4, 29 (35.4%) (P <.001). The rate of SGA was higher in group 3 compared with group 1. Preeclampsia differed among groups 1 (85 [4.6%]), 2 (9 [7.6%], 3 (7 [5.5%]), and 4 (15 [18.3%]) (P <.001). CONCLUSION: Pregnancy outcomes in women with abnormal uterine artery Doppler results at either 20 or 24 weeks were intermediate between those with normal or abnormal results at both time points. If overall test performance could be enhanced by the addition of clinical data, biomarkers, or both, we would recommend that 20 weeks is the most appropriate gestation in the second trimester to perform uterine artery Doppler studies.