Advanced maternal age is a risk factor for both early-onset and late-onset hypertensive disorders of pregnancy: the Japan environment and children's study.

OBJECTIVE Advanced maternal age (AMA, ≥35 years), particularly prevalent in Japan, is associated with adverse perinatal outcomes, including hypertensive disorders of pregnancy (HDP), which vary in severity based on the timing of onset (early-onset and late-onset). This study aimed to investigate the association between maternal age and early-onset and late-onset HDP.

METHODS A total of 80,872 pregnant women were included in this prospective birth cohort study. Associations between maternal age and early-onset, preterm late-onset, and term late-onset HDP were evaluated using a multinomial logistic regression model adjusted for potential confounding factors. Maternal age was categorized into five: <25, 25‒29.9, 30‒34.9, 35‒39.9, and ≥40 years, with the reference category set as 30‒34.9 years.

RESULTS Higher maternal age was significantly associated with increased odds of developing early-onset, preterm late-onset, and term late-onset HDP. The adjusted odds ratios (aORs) for early-onset HDP in women aged 35‒39.9 and ≥40 years were 2.724 (95% confidence interval [CI]: 2.095-3.542) and 3.493 (95% CI: 2.349-5.196), respectively. Regarding preterm late-onset HDP, the aORs were 1.346 (95% CI: 1.057-1.714) and 3.011 (95% CI: 2.171-4.176) for these age groups, respectively. Similarly, the aORs for term late-onset HDP were 1.417 (95% CI: 1.206-1.664) and 1.762 (95% CI: 1.341-2.316), respectively.

CONCLUSION Higher maternal age was associated with an increased HDP risk, irrespective of diagnosis timing. Associations between maternal age and early-onset and preterm late-onset HDP were stronger than that with t erm late-onset HDP.