NPPB and heart failure: In a normal pregnancy, the biomarker N-terminal pro-B-type natriuretic peptide (NT-proBNP) should remain within normal limits throughout all three trimesters; an elevation above 200 pg/mL is associated with an increased risk of heart failure or preeclampsia.23 In pregnant women with stable valvular disease, NT-proBNP levels are often elevated above normal limits but should remain stable throughout pregnancy.