Advanced maternal age elevates the prevalence of hypertensive disorders in women of Japanese, independent of blood pressure: a study from the Japan Environment and Children's study.

Hypertensive disorders of pregnancy (HDP) are leading causes of maternal and infant mortality, and maternal age is a known factor influencing maternal and pediatric outcomes during childbirth. This study aimed to clarify the impact of maternal age-specific blood pressure (BP) and its patterns on the risk of HDP using data from a large nationwide study in Japan. This cohort study (N = 100,949) used data from the Japan Environment and Children's Study. The outcome variables in this study were HDP at each trimester of pregnancy. We stratified the participants into groups according to their age. The risk of HDP tended to be higher in women aged ≥35 years than in those aged <35 years, even at the same BP level. The BP patterns in the first and second trimesters of pregnancy showed a significantly increased risk of developing HDP at a higher BP in the first trimester, even when the BP in the second trimester was the same. The risk of HDP was equivalent in women aged <35 years and those aged≥ 35 years with an approximately 10 mmHg lower BP. In contrast, in women aged ≥35 years, a low diastolic BP in early pregnancy and pulse pressure (PP) > 60 mmHg significantly increased the risk of HDP. This large national cohort study indicates that the risk of HDP is associated with maternal age and PP in Japan. Early diagnosis of HDP can be achieved by focusing on the BP in the first trimester of pregnancy and PP.