(880) Decreased Second Trimester Blood Pressure Nadir is Associated with Gestational Hypertensive Disease

It is well known that a physiologic blood pressure (BP) nadir occurs during the 2^nd trimester (Tri2). Whether an inhibited blood pressure nadir is associated with the development of hypertensive disorders of pregnancy (HDP) is less clear. We investigated if decreased Tri2 BP nadir associates with gestational hypertensive disease (GHDP) development.

Study Design:

We conducted a retrospective cohort study utilizing a clinical database at a racially diverse, urban, safety-net hospital. Subjects ages 18-40 with a singleton gestation & 1^st trimester (Tri1) prenatal care were included. Those with chronic hypertension were excluded. Gestational hypertension (GHTN) and preeclampsia with & without severe features (PREWSF, PREWOSF) were diagnosed based on ACOG criteria & constituted GHDP. Systolic BP (SBP), diastolic BP (DBP), & mean arterial pressure (MAP) nadir were calculated (Tri2 SBP/DBP/MAP-Tri1 SBP/DBP/MAP) & compared between subjects with & without GHDP. Tests for normality, Kruskal-Wallis tests, & multivariable linear regression with adjustment for confounders were performed.

Results:

Of N=3,354 subjects, 18% had GHDP.  Mean gestational age of Tri1 and Tri2 BP values were 9.8±2.1 & 23.5 ± 2.3 weeks. Among those with GHDP vs without, Tri1 SBP (p < 0.01), DBP (p < 0.01), & MAP (p < 0.01) were significantly higher (Table 1). Among those with GHDP vs without, mean change in SBP (-1.7 ± 12.3 vs -2.9 ± 11.8, p< 0.001) & MAP (-2.1 ± 8.4 vs -2.7 ± 7.9, p=0.01) were significantly lower, identifying a mitigated SBP/MAP nadir (Figure 1). Among those with GHDP vs without, mean change in DBP trended lower (-2.3 ± 8.7 vs -2.7 ± 8.2, p=0.19) (Figure 1). Significant differences for SBP & MAP were maintained when controlling for age, race, substance use, & body mass index (p < 0.01).

Conclusion:

Inhibited physiologic Tri2 BP nadir suggests vascular dysregulation. Our data suggest that those with GHDP vs those without have decreased SBP & MAP nadir. These data are foundational for future studies to utilize noninvasive hemodynamic monitoring measures to understand how vascular regulation can predict & potentially prevent HDP.