Evaluation of B-type Natriuretic Peptide (BNP) Levels in Normal and Preeclamptic Women

Objective: B-type natriuretic peptide (BNP) is synthesized in cardiac ventricles in response to volume expansion. This study evaluated BNP levels to determine trends during pregnancy, and to assess BNP as a diagnostic tool in preeclampsia.

Study Design: We studied 163 BNP levels in 118 pregnant women, ranging from first trimester to term. An additional 34 patients with preeclampsia were studied and compared to 25 normal control patients at term. Plasma BNP values were determined using a standard assay.

Results: The median BNP levels during the 1st, 2nd, 3rd trimester, and at term were equivalent (18.4, 17.9, 15.5, and 17.8 pg/mL, respectively, P = .796). The median BNP levels in normal patients, mild preeclamptics, and severe preeclamptics were 17.8, 21.1, and 101 pg/mL, respectively, with the severe group being significantly higher than the mild group (P = .003) and any phase of normal pregnancy (P < .001 in each case). A BNP cut-off of <40.6 pg/mL had a negative predictive value of 92% in excluding preeclampsia.

Conclusion: In normal pregnancies, median BNP values are <20 pg/mL, and stable throughout gestation. In severe preeclampsia BNP levels are elevated. This may reflect ventricular stress and/or subclinical cardiac dysfunction associated with preeclampsia.