Prevalence and risk factors of labor-onset hypertension: A multicenter study in Japan.

Objectives: To investigate the prevalence and risk factors of labor-onset hypertension (LOH), defined as hypertension first detected during labor among women without hypertension prior to admission for labor.

Study Design: In this multicenter retrospective study, clinical data of women who delivered vaginally at term between 2012 and 2018 were collected from 12 primary maternity care units. Blood pressure was measured at five time points from admission to 2 h postpartum in a total of 30,129 normotensive women at the last prenatal check-up. LOH was defined as systolic blood pressure (SBP) of ≥ 140 mmHg or diastolic blood pressure (DBP) of ≥ 90 mmHg during the first to fourth stages of labor.

Main Outcome Measures: Multivariate regression analyses were conducted to evaluate the risk factors of LOH and severe LOH (SBP of ≥ 160 mmHg or DBP of ≥ 110 mmHg).

Results: Among the 30,129 women, 8,565 (28.4%) presented with LOH and 734 (2.4%) with severe LOH. The prevalence of LOH was the highest at the second stage of labor (21.7%) and decreased rapidly after delivery. The independent risk factors of LOH were maternal age of ≥ 35 years, pre-pregnancy body mass index of ≥ 25 kg/m, and pregnancy weight gain of ≥ 15 kg.

Conclusion: LOH is common, with approximately one in four women experiencing LOH during labor and early postpartum. Meanwhile, severe LOH occurred in 2.4% of the pregnancies. Closer blood pressure monitoring during labor may enable obstetric caregivers to recognize LOH in a timely manner and reduce maternal adverse outcomes, such as eclampsia and stroke.