Longitudinal changes in the B-type natriuretic peptide levels in normal pregnancy and postpartum.

Normal levels of B-type natriuretic peptide (BNP) are not well established in pregnancy. We obtained longitudinal BNP levels in 29 healthy pregnant women in each trimester and postpartum period, and compared these levels to the 25 nonpregnant controls. There were no significant differences among the cases and controls with respect to weight, diastolic blood pressure, and ethnicity. A total of 116 BNP values were obtained during pregnancy. The median (and range) BNP level during pregnancy was 19 (10-143) pg/ml versus 10 (10-37) pg/ml in the nonpregnant controls (p = 0.003). However, there were no statistically significant differences in the median BNP levels at various stages of pregnancy: first trimester 20 (10-115) pg/ml versus the second trimester 18 (10-112) pg/ml (p = 0.8), second trimester 18 pg/ml versus third trimester 26 (10-143) pg/ml (p = 0.06), and third trimester 26 pg/ml versus postpartum18 (10-62) pg/ml (p = 0.08). There were no significant differences between the BNP levels throughout the trimesters and postpartum period. Pregnant BNP levels were approximately twice as high as the nonpregnant BNP levels. Our study is unique in evaluating longitudinal changes in BNP levels in normal pregnancies and the postpartum period in comparison with healthy, nonpregnant controls. It demonstrates that pregnant BNP levels are approximately 2-fold higher than their nonpregnant counterparts, and do not significantly fluctuate during pregnancy. In conclusion, pregnancy is associated with a significant, but small increase in the BNP levels compared with nonpregnant women.