OBJECTIVE: To estimate the pattern of maternal vascular reactivity in normal a nd high-risk pregnancies using postocclusion brachial artery diameter. METHODS: Prospective, longitudinal study of 44 low-risk singleton pregnancies and 28 hi gh-risk pregnancies, defined as pregestational diabetes (n = 7), chronic hypert ension (n = 4), twin gestation (n = 6), and a previous history of preeclampsia, fetal growth restriction, or vascular disease (n = 11). During each trimester, t he brachial artery was ultrasonographically imaged above the antecubital crease. Brachial artery diameter was measured and then occluded for 5 minutes using an inflated blood pressure cuff. Changes in brachial artery diameter at 1 minute af ter occlusion were expressed as percent change from baseline and were compared a cross trimesters for both low-risk and high-risk groups, adjusting for potenti al confounders. RESULTS: Brachial artery diameters were increased after occlusio n in every trimester for all groups. For low-risk women, the degree of postoccl usion brachial artery dilatation was similar in the first and second trimesters, but was lower in the third trimester. In the first trimester, low-risk women h ad significantly greater brachial artery diameter increases at 1 minute compared with high-risk singleton pregnancies (19%compared with 12%; P < .001). Compa red with low-risk women, pregnancies complicated by pregestational diabetes or chronic hypertension had significantly smaller 1-minute brachial artery diamete r changes in the first trimester (7.0 ±0.5%, P < .001), whereas twin gestation s had greater brachial artery responses (22.9 ±6.0%, P < .001). Women with pre vious preeclampsia or vascular disease had responses similar to low-risk women. CONCLUSION: Maternal vascular reactivity as assessed by postocclusion brachial artery dilatation decreases in the third trimester in both low-risk and high-r isk women. In addition, singleton pregnancies at high risk for preeclampsia disp lay decreased brachial artery reactivity compared with low-risk women.
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