Nocturnal systolic and diastolic blood pressure across gestational periods and the risk of preeclampsia.

To investigate the relationship between blood pressure (BP) components (daytime vs. nocturnal BP and systolic vs. diastolic BP) and preeclampsia (PE) across gestational stages. We conducted a historical cohort study involving 1363 high-risk pregnant women (mean age, 30 ± 7 years). Ambulatory BP monitoring (ABPM) was performed at 12-19 weeks (n = 389), 20-27 weeks (n = 798), and 28-36 weeks (n = 1176); 59.9, 25.0, and 15.1% of the participants underwent one, two, and three ABPM evaluations, respectively. PE occurred in 15.4, 18.9, and 20.2% of the women evaluated at 12-19, 20-27, and 28-36 weeks, respectively. In the second half of pregnancy, sustained (daytime and nighttime) and isolated nocturnal hypertension were strong predictors of PE. Conversely, before the 20th week of gestation, only sustained hypertension (but not isolated nocturnal hypertension) increased PE risk, with lower odds ratios (ORs). Moreover, the areas under the curve (AUCs) for all ABPM components increased markedly after the 20th week of gestation. In late pregnancy, systolic and diastolic ABPM levels as well as all forms of nocturnal hypertension (isolated systolic, isolated diastolic, and combined systodiastolic) were significantly associated with PE risk, with ORs remaining significant after adjusting for daytime ABPM and maternal covariates. Patients with systodiastolic nocturnal hypertension had the highest risk. Conversely, neither daytime hypertension nor daytime ABPM levels remained statistically significant after adjusting for nocturnal ABPM levels. In conclusion, the association between PE and systolic, diastolic, and systodiastolic nocturnal hypertension emerges in the second half of pregnancy, suggesting a relationship with abnormal placentation.