(791) Use of standing blood pressures in pregnant patients with chronic hypertension

This was a prospective observational study at a large academic medical center from May 2024-June 2025 of pregnant individuals at a maternal-fetal medicine clinic specializing in chronic hypertension. At each prenatal visit, BP was measured in seated and standing positions. Patients rested in a seated position before the first measurement, then stood for one minute before the standing measurement. Values from each visit were analyzed across gestation using random effects repeated measures models, reporting means and 95% confidence intervals. A sample size of 338 patients was estimated to detect a 3mmHg difference in seated vs standing BP with 80% power.

Results:

There were 360 patients with chronic hypertension who met inclusion criteria, enrolled, and delivered during the study period. At entry to prenatal care, 106 (29.6%) were on antihypertensive therapy (Table 1). Seated systolic BP (SBP) was 3.5 mmHg higher than standing, with this difference increasing across gestation (Figure 1, p< 0.001). Early in pregnancy, seated diastolic BP (DBP) was 2 mmHg lower than standing (p< 0.001), with this difference diminishing with advancing gestation. Among 102 (30.2%) patients who developed superimposed severe preeclampsia, difference in SBP for seated vs standing was significantly higher than in those without severe preeclampsia (5.0 ± 6.1 vs 3.1 ± 7.3 mmHg, p=0.012).

Conclusion:

In a prospective longitudinal study of pregnant individuals with chronic hypertension, standing BP measurements differ significantly from seated values, with standing SBP lower throughout gestation. This difference appears more pronounced in those who go on to develop superimposed severe preeclampsia, suggesting potential prognostic value of using standing BPs for earlier risk stratification.