B-type natriuretic peptide and echocardiography reflect volume changes during pregnancy

To evaluate B-type natriuretic peptide (BNP) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) and cardiac structure and function in normal women through pregnancy and the postpartum.

In this prospective observational study, we obtained serial transthoracic echocardiograms, BNP, and NT-proBNP at seven intervals from 6 weeks' gestation through 12 months postpartum. Women with hypertension or cardiac disease were excluded. Using 6-12 months postpartum as reference for non-pregnant levels, echocardiogram measurements and BNP/NT-proBNP were compared over time using linear mixed models with Tukey-Kramer adjustment for multiple comparisons.

Of 116 patients, data was available for 78-114 healthy pregnant or postpartum women within each time interval, and 102 patients provided data for ≥4 intervals. Compared to 6-12 months postpartum, BNP and NT-proBNP remained stable through pregnancy and delivery, increased within 48 h postpartum (P<0.0001), then returned to baseline. Left ventricular volume increased within 48 h postpartum (P=0.021) while left atrial volume increased at 18-24 weeks (P=0.0002), 30-36 weeks (P<0.0001) and within 48 h postpartum (P=0.002). The transmitral early/late diastolic velocity (E/A) ratio, transmitral early/peak mitral annulus diastolic velocity (E/E') ratio, isovolumic relaxation times, and mitral valve deceleration times were similar within 48 h and 6-12 months postpartum.

In normal women, BNP/NT-proBNP, left atrial, and left ventricular volumes increase within 48 h postpartum without indications of altered diastolic function.