(1128) Admission BNP Level and Postpartum Blood Pressure Prior to Discharge

We sought to evaluate the relationship between brain natriuretic peptide (BNP) levels at the time of admission for delivery and postpartum blood pressures (BP) prior to discharge.

Study Design:

This was a prospective cohort of patients admitted for delivery with a diagnosis of hypertensive disorders of pregnancy (HDP; n= 57) or with known risk factors without a diagnosis on admission of HDP (n=103). Risk factors included diagnosis of HDP in a prior pregnancy, chronic hypertension, diabetes, obesity, excess gestational weight gain, assisted reproductive technology, advanced maternal age, nulliparity and late term gestation (> 41 weeks). BNP and maternal weight were measured at admission. Postpartum weight and the highest systolic and diastolic BP were collected for each day through discharge. Our primary outcome was systolic BP on postpartum day 2, testing the hypothesis that it would be predicted by an elevated admission BNP(BNP>50 pg/mL). Our planned sample size was 134 patients, with 67 patients in each group (alpha 0.05 and power of 0.9). Categorical variables of patients with BNP of <50 pg/mL and >50 pg/mL were compared using chi-square and Fisher exact while continuous variables were compared using two sample t- test and Wilcoxon rank sum test.

Results: Of 160 patients enrolled in the study, 23 (14.4%) patients had a BNP >50 pg/mL. Rates of HDP differed on admission (43.5% vs 34.3%;p=.04), intrapartum (65.2% vs 46%;p=.002), and postpartum (69.6% vs 51.8%; p=.002) between patients with admission BNP levels >50 pg/mL and patients with admission BNP levels <50 pg/mL. Patients with admission BNP levels >50 pg/mL had higher median peak systolic and diastolic BP on both postpartum day 1 (144 vs 127, p=.0003; and 87 vs 80, p=.0005) and day 2 (134 vs 126, p=0.014; and 84 vs 79, p=0.049) when compared to patients with admission BNP levels <50 pg/mL.

Conclusion:

Despite inadequate sample to appropriately power this study and assess the role of confounding factors, elevated BNP levels on admission appears to predict higher BP in the immediate postpartum period.