First-trimester mean arterial pressure and risk of preeclampsia.

BACKGROUND Maternal second-trimester mean arterial pressure (MAP) is associated with a risk of preeclampsia in some but not all published studies. We examined average first-trimester MAP in relation to preeclampsia risk among 1655 women. METHODS Using blood-pressure measurements recorded during prenatal care, we calculated MAP, and averaged the values within the first trimester. We defined preeclampsia according to national criteria, using information abstracted from medical records. We classified participants by MAP quartiles: <79, 79-83, 84-88, and >or=89 mm Hg. We calculated risk ratios (RRs) and 95% confidence intervals (CIs) adjusted for prepregnancy body mass index, age, race/ethnicity, and parity. RESULTS High-quartile MAP was associated with an increased risk of preeclampsia when using current diagnostic criteria (adjusted RR versus low-quartile, 3.0; 95% CI, 1.2-7.4) but not when using older criteria (RR, 1.2; 95% CI, 0.6-2.2). First-trimester MAP did not strongly predict future preeclampsia (area under the receiver operating curve, 0.71). A MAP >/=88 mm Hg predicted preeclampsia with a sensitivity of 0.78 and a specificity of 0.63. CONCLUSIONS Although first-trimester MAP is strongly associated with risk of preeclampsia, it poorly discriminates between women who will and will not develop the disease.