Nocturnal hypertension and risk of developing early-onset preeclampsia in high-risk pregnancies.

To test the hypothesis that nocturnal hypertension identifies risk for early-onset preeclampsia/eclampsia (PE), we conducted an historical cohort study of consecutive high-risk pregnancies between 1st January 2016 and 31st March 2020. Office blood pressure (BP) measurements and ambulatory blood pressure monitoring (ABPM) were performed. The cohort was divided into patients without PE or with early- or late-onset PE (<34 and ≥34 weeks of gestation, respectively). The relative risks of office and ABPM hypertension for the development of late- or early-onset PE were estimated with multinomial logistic regression using no PE as a reference category. Four hundred and seventy-seven women (mean age 30 ± 7 years, with 23 ± 7 weeks of gestation at the time of the BP measurements) were analyzed; 113 (23.7%) developed PE, 69 (14.5%) developed late-onset PE, 44 (9.2%) developed early-onset PE. Office and ambulatory BP increased between the groups, and women who developed early-onset PE had significantly higher office and ambulatory BP values than those with late-onset PE or without PE. Hypertension prevalence increased across groups, with the highest values in early-onset PE. Nocturnal hypertension was the most prevalent finding and was highly prevalent in women who developed early-onset PE (88.6%); only 1.6% of women without nocturnal hypertension developed early-onset PE. Additionally, nocturnal hypertension was a stronger predictor for early-onset PE than for late-onset PE (adjusted OR, 5.26 95%CI 1.67-16.60) vs. 2.06, 95%CI 1.26-4.55, respectively). In conclusion, nocturnal hypertension was the most frequent BP abnormality and a significant predictor of early-onset PE in high-risk pregnancies.