Impact of cumulative blood pressure load during early pregnancy on the risk of low birth weight: the BOSHI study

This study investigated the association between cumulative blood pressure (BP) load, defined as the area above a threshold reflecting the duration and magnitude of BP elevation, and low birth weight (LBW). We included 729 pregnant women in this prospective cohort study. Home BP measurements collected at 10 weeks 0 days and 15 weeks 6 days were assessed. The participants were classified into three groups based on their cumulative BP load: (1) no cumulative BP load elevation, (2) isolated cumulative BP load elevation (with normal average BP), and (3) high average BP (average BP above the normal range). Normal ranges (systolic BP < 115 mmHg, diastolic BP < 75 mmHg) were defined following the guidelines; BP load threshold (systolic BP < 104 mmHg, diastolic BP < 62 mmHg) was set using median averages. The mean age at pregnancy was 31.2 years, and 54.4% were primiparas. The mean birth weight was 3060 g; 47 newborns had LBW. The groups with isolated cumulative systolic BP load elevation (risk ratio [RR]: 2.86, 95% confidence interval [CI]: 1.33-6.17) and high average systolic BP (RR: 3.57, 95% CI: 1.38-9.24) showed higher LBW risk than the group without cumulative systolic BP load elevation. Similar associations were observed for cumulative diastolic BP load elevation (RR: 2.22, 95% CI: 1.08-4.58) and high average diastolic BP (RR: 3.35, 95% CI: 1.08-10.34). Our findings highlight the significance of monitoring home BP and the utility of the cumulative BP load in evaluating LBW risk. This study evaluated the association between cumulative blood pressure (BP) load elevation during early pregnancy and the risk of low birth weight (LBW). Elevation of both cumulative systolic and diastolic BP load was associated with an increased risk of LBW, even when average BP remained within the normal range.