NT-proBNP, a marker of ventricular dysfunction, varies by BMI outside of pregnancy with a lower threshold proposed for obesity. We sought to compare NT-proBNP levels between healthy obese and non-obese pregnant women. Prospective observational study of healthy pregnant women in the 3rd and 4th trimesters. Subjects were excluded if they had significant medical comorbidities or if their fetus had anomalies, growth restriction or aneuploidy. NT-proBNP was measured at 28 weeks(3TM), prior to delivery(PD), 1-2 days postpartum(IP), and 4-6 weeks postpartum(PP). LogNT-proBNP at these time points was analyzed using linear mixed effects models, including BMI< or ≥30, time, and time-by-BMI interactions with adjustment for hypertensive disorders of pregnancy (PIH) and race. 55 pregnant women (28 BMI≥30 and 27 BMI<30) enrolled. Obese women were more likely to develop PIH (50% vs 15%, p=0.010), be black (75% vs 29.6%, p=0.002), and have higher systolic blood pressure at all time points (p <0.05). Median NT-proBNP in pg/mL was 18 vs 26 at 3TM, 16 vs 43 at PD, 58 vs 63 at IP, and 33 vs 23 at PP for obese vs non-obese women (Figure 1). In linear mixed effects models, logNT-proBNP was significantly lower in obese women at 3TM (β=-0.89, 95%CI -1.51, -0.26) and PD (β=-1.05, 95%CI -1.72, -0.38) and trended lower IP (β=-0.52, 95%CI -1.16, 0.13; Table 1). The logNT-proBNP trends over time differed by BMI category, with higher values in obese women at both postpartum time points compared to the 3TM (IP β=1.24, 95% CI 0.75, 1.73); PP β=1.08, 95%CI 0.52, 1.63), but only IP for non-obese women (β=0.87, 95%CI 0.36, 1.38). Obese women have significantly lower NT-proBNP than non-obese women during pregnancy, but not postpartum. While NT-proBNP increases in the immediate postpartum period in obese and non-obese women, this increase persists to 4-6 weeks postpartum for obese women. These findings suggest that healthy obese pregnant women have lower baseline NT-proBNP levels than non-obese women, but that their cardiac recovery postpartum may be more prolonged.View Large Image Figure ViewerDownload Hi-res image Download (PPT)