NT-proBNP Levels and Obesity in Pregnancy

A screening modality to help categorize obese pregnant women as high or low probability for heart failure would be helpful in the evaluation of the obese pregnant women with dyspnea. Outside of pregnancy, measurement of brain natriuretic peptide (BNP) or amino-terminal pro-brain natriuretic peptide (NT-proBNP) is recommended in the evaluation of acute dyspnea and in the diagnosis of heart failure. During pregnancy, elevated BNP has been associated with adverse cardiovascular events, while normal BNP levels have been observed in healthy pregnancies. While BNP levels outside of pregnancy have been shown to be lower in obese patients variations in BNP levels by body mass index (BMI) in pregnancy have not been studied. Before BNP can be deemed a reliable screening test for heart failure in obese pregnant women, normal BNP values in the setting of obesity and pregnancy need to be established. We therefore propose the following specific aims: Objective 1: Compare mean plasma NT-proBNP levels in the third trimester, immediately postpartum, and at 4-6 weeks postpartum between obese pregnant women without cardiovascular disease and non-obese pregnant women without cardiovascular disease. We hypothesize that mean plasma NT-proBNP levels in obese pregnant women without pre-existing cardiovascular disease will be significantly lower than levels in non-obese pregnant women. Objective 2: Assess whether plasma NT-proBNP levels in pregnancy correlate with BMI. We hypothesize that there will be an inverse correlation between plasma NT-proBNP levels and BMI in our pregnant cohort similar to that seen outside of pregnancy.