The relationship between high-normal blood pressure in the first half of pregnancy and the risk of hypertensive disease of pregnancy

Early warning of hypertensive disorder in pregnancy (HDP) can improve maternal and infant outcomes. However, few studies had evaluated the warning value of high-normal blood pressure (BP) before the onset of HDP. This was a prospective cohort study to investigate the relationship between high-normal BP in the first half of pregnancy and the risk of HDP. According to the maximum BP measured before 20(+6) weeks of gestation, the cohort was divided into three groups: optimal BP (SBP < 120 mmHg and DBP < 80 mmHg), normal BP (120 mmHg <= SBP < 130 mmHg or 80 mmHg <= DBP < 85 mmHg), and high-normal BP (130 mmHg <= SBP < 140 mmHg or 85 mmHg <= DBP < 90 mmHg). The relationship between different BP levels in the first half of pregnancy and HDP risk was assessed by general linear models. Ten thousand one hundred and ninety-three normotensive pregnant women with complete information were finally included for data analysis. Among them, 532 pregnant women were diagnosed with HDP, with a total HDP incidence of 5.2%. The incidences in the optimal, normal, and high-normal BP groups were 2.4%, 6.0%, and 21.8%, respectively. Compared to women with optimal BP in the first half of pregnancy, women with high-normal BP had a 445% increased risk of HDP (aRR: 5.45, 95% CI: 4.24-7.00), and even women with normal BP had a 107% increased risk of HDP (aRR: 2.07, 95% CI: 1.68-2.56). This study demonstrated that among low-risk healthy women, women with high-normal BP in the first half of pregnancy had a significantly higher risk of HDP.