Plasma concentrations of N-terminal Pro-B-Type natriuretic peptide in pregnant women near labor and during early puerperium.

To the Editor: B-Type natriuretic peptide (BNP) is considered an important component of the adaptive mechanism that helps reduce the load on the myocardium through systemic vasodilatation, reduction in venous return, and reduction in vascular volume (1). Plasma concentrations of BNP have been shown to reflect cardiac dysfunction and volume overload in adults and children (2– 4). BNP is synthesized in cardiac myocytes as a prohormone, proBNP. The active hormone, BNP, is cleaved and cosecreted from the myocyte along with its N-terminal propeptide (NT-proBNP) (5). NT-proBNP concentrations have been shown to provide information similar to BNP, and the validity of the assay as a clinical tool is well documented (3, 6 –9). Pregnancy represents a state of physiologic volume expansion as maternal blood volume increases ϳ40%– 45% above nonpregnancy volumes (10). Despite the growing data on the role of BNP in regulation of volume homeostasis, there are few studies regarding its role in pregnancy (11–14). It has been shown that BNP concentrations are higher in preeclampsia and other hyperten-sive disorders of pregnancy than in normal pregnancy (11, 12, 14). It has also been suggested that BNP may have a role in regulation of amniotic fluid volume (15). Because NT-proBNP may be used as a marker for various pathologic conditions in pregnancy and the pu-erperium, we conducted a study to determine reference values for NT-proBNP in pregnant women near delivery and in the early postpartum period. The study was approved by the hospital ethics committee. A total of 88 healthy women admitted to the delivery room at Hadassah Mt. Sco-pus hospital were enrolled in the study. After receipt of informed consent , blood samples were collected (during admission to the labor ward and within 28 h after delivery). For reference values, all measurements were included. For comparison and correlation between the pre-and postpartum states, only paired sets of measurements were considered. For each patient, demographic details, obstetric history, and current pregnancy details were recorded. NT-proBNP was measured with an electrochemiluminescence immu-noassay for proBNP (Roche) on the Elecsys 1010/2010 system. NT-proBNP results are presented as the mean (SD). Mean maternal age was 30.5 (range, 18 – 43) years, and the mean gestational age was 39.5 (35– 42) weeks. The mean birth weight was 3237 (2200 – 4255) g. For 62 women, paired samples were available for analysis, whereas for 26, only one blood sample was available (14 collected before delivery and 12 …