First-trimester risk factors for preeclampsia development in women initiating aspirin by 16 weeks of gestation.

OBJECTIVE: The residual risk of preeclampsia in high-risk women on aspirin prophylaxis exceeds that of low-risk populations, and this study aimed to identify first-trimester maternal characteristics associated with aspirin prophylaxis failure. METHODS: This is a nested cohort study of prospectively enrolled women with verified initiation of risk-indicated aspirin prophylaxis by 16 weeks of gestation. First-trimester maternal history, demographics, anthropometry, ultrasound parameters, and serum analytes were compared between women who developed preeclampsia and those who did not. Blood pressure measurements were classified as prehypertension or hypertension according to the Joint National Committee on Hypertension guidelines. Chi square, nonparametric, and logistic regression analyses were used to determine the contributors to preeclampsia development. RESULTS: Six hundred fourteen women prospectively enrolled at 9-14 weeks of gestation initiated aspirin by 16 weeks of gestation. The 59 (9.6%) women who developed preeclampsia were more likely to have chronic hypertension, diabetes, and obesity and had higher first-trimester blood pressure and lower serum pregnancy-associated plasma protein-A concentrations (all P<.05). Having first-trimester Joint National Committee on Hypertension prehypertension or hypertension was associated with a 2.18-fold increased risk of developing preeclampsia, whereas normotension was associated with a reduction of risk of 56%. CONCLUSION: Women who develop preeclampsia while taking aspirin prophylaxis are more likely to have elevated first-trimester blood pressures. Conversely, first-trimester normotension is associated with a reduced risk of preeclampsia.