Printer Friendly

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 ~40%-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 hypertensive 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 puerperium, 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. Scopus 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 preand 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 immunoassay 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 postpartum). NT-proBNP concentrations in the nonpaired groups were distributed similarly to those in the paired samples and therefore are comparable.

The mean (SD) maternal blood NT-proBNP concentration was 81 (32) ng/L before delivery and 165 (102) ng/L after delivery (n = 62; P <0.001).

We found no correlation between maternal blood NT-proBNP concentrations before and after delivery to parity, duration of labor, or birth weight of the offspring. There was a weak correlation between maternal blood NT-proBNP concentrations before delivery and gestational week (r = 0.226; P <0.05; n = 76), but no such correlation was found after delivery.

Women who received analgesia during labor (epidural, pethidine, or inhaled [N.sub.2]O) had significantly higher NT-proBNP concentrations before delivery than did those who did not use analgesia: 92 (48) ng/L (n = 56 of 76) vs 69 (26) ng/L (n = 20 of 76), respectively (P = 0.041). However, we found no postdelivery difference between the 2 groups.

Women who did not undergo induction or augmentation of labor had significantly higher postdelivery concentrations of NT-proBNP than did those who underwent induction: 181 (116) ng/L (n = 50 of 74) vs 116 (70) ng/L (n = 24 of 74), respectively (P = 0.004). However, we found no difference in predelivery concentrations between the 2 groups.

Human pregnancy represents a state of physiologic volume expansion, as maternal blood volume increases markedly. By 1 week after delivery, the blood volume returns nearly to its nonpregnancy value (16), and the mean weight loss of 2-3 kg during this week is attributed to diuresis. The 2-fold increase in NT-proBNP after delivery suggests that BNP may be involved in postpartum diuresis. Recently, it was found that BNP mRNA of the left ventricle was increased in postpartum rats. The authors of that study concluded that natriuretic peptides may be involved in the adaptation to volume alterations associated with pregnancy (17).

In our study cohort, NT-proBNP concentrations before and after delivery were not influenced by parity, gestational age, or duration of delivery. Concentrations after delivery were not influenced by the use of analgesia; although pethidine and nitric oxide depress myocardial contractility, we found no difference in NT-proBNP concentrations after delivery between women who received these medications and those who did not.

Women who subsequently used analgesia during their delivery had significantly higher NT-proBNP concentrations on admission than did those who did not use any form of analgesia during labor. Because analgesia is given to those who demand it, this difference may be a result of variations in pain perception, i.e., women whose threshold is lower feel unbearable pain at earlier stages during delivery and require analgesia. As pain is accompanied by increased sympathetic tone and other mediators, this may lead to higher NT-proBNP concentrations before delivery than in those women whose pain was bearable.

Predelivery NT-proBNP concentrations did not differ between women who were having labor induced and women admitted in active labor, but in those women who did not have labor induced, postdelivery NT-proBNP concentrations were higher. We cannot explain these results, as we would expect that women presenting in active labor would have higher NT-proBNP concentrations before labor than would those who were admitted for induction of labor because cardiac output increases moderately during the first stage of labor and even more during the second stage (18). Furthermore, we would not expect any difference in NT-proBNP concentrations after delivery because the hemodynamic changes are similar.

Our results may be used as a basis for establishing assay-specific reference values for NT-proBNP in women before and after labor. This may enable physicians to use the concentrations of this hormone as a marker for normal transition and, more importantly, to help identify pathologic conditions such as pulmonary embolism and postpartum cardiomyopathy. To achieve these goals, larger scale studies would be necessary.

References

(1.) Bonow RO. New insights into the cardiac natriuretic peptides. Circulation 1996;93: 1946-50.

(2.) Troughton RW, Frampton CM, Yandle TG, Espiner EA, Nicholls MG, Richards AM. Treatment of heart failure guided by plasma aminoterminal brain natriuretic peptide (N-BNP) concentrations. Lancet 2000;355:1126-30.

(3.) Nir A, Bar-Oz B, Perles Z, Brooks R, Korach A, Rein AJ. N-terminal pro-B-type natriuretic peptide: reference plasma levels from birth to adolescence. Elevated levels at birth and in infants and children with heart diseases. Acta Paediatr 2004;93:603-7.

(4.) Clerico A, Emdin M. Diagnostic accuracy and prognostic relevance of the measurement of cardiac natriuretic peptides: a review. Clin Chem 2004;50:33-50.

(5.) de Lemos JA, McGuire DK, Drazner MH. B-Type natriuretic peptide in cardiovascular disease. Lancet 2003;362:316-22.

(6.) Hammerer-Lercher A, Neubauer E, Muller S, Pachinger 0, Puschendorf B, Mair J. Head-to-head comparison of N-terminal pro-brain natriuretic peptide, brain natriuretic peptide and N-terminal pro-atrial natriuretic peptide in diagnosing left ventricular dysfunction. Clin Chim Acta 2001;310:193-7.

(7.) Goetze JP, Kastrup J, Pedersen F, Rehfeld JF. Quantification of pro-B-type natriuretic peptide and its products in human plasma by use of an analysis independent of precursor processing. Clin Chem 2002;48:1035-42.

(8.) Mair J. Role of cardiac natriuretic peptide testing in heart failure. Clin Chem 2002;48:977-8.

(9.) Mueller T, Gegenhuber A, Poelz W, Haltmayer M. Comparison of the Biomedica NT-proBNP enzyme immunoassay and the Roche NT-proBNP chemiluminescence immunoassay: implications for the prediction of symptomatic and asymptomatic structural heart disease. Clin Chem 2003;49:976-9.

(10.) Whittaker PG, Macphail S, Lind T. Serial hematologic changes and pregnancy outcome. Obstet Gynecol 1996;88:33-9.

(11.) Itch H, Sagawa N, Mori T, Mukoyama M, Nakao K, Imura H. Plasma brain natriuretic peptide level in pregnant women with pregnancy-induced hypertension. Obstet Gynecol 1993;82: 71-7.

(12.) Furuhashi N, Kimura H, Nagae H, Yajima A, Kimura C, Saito T. Brain natriuretic peptide and atrial natriuretic peptide levels in normal pregnancy and preeclampsia. Gynecol Obstet Invest 1994;38:73-7.

(13.) Borghi C, Esposti DD, Immordino V, Cassani A, Boschi S, Bovicelli L, et al. Relationship of systemic hemodynamics, left ventricular structure and function, and plasma natriuretic peptide concentrations during pregnancy complicated by preeclampsia. Am J Obstet Gynecol 2000;183:140-7.

(14.) Fleming SM, O'Byrne L, Grimes H, Daly KM, Morrison JJ. Amino-terminal pro-brain natriuretic peptide in normal and hypertensioe pregnancy. Hypertens Pregnancy 2001;20: 169-75.

(15.) Bajoria R, Ward S, Chatterjee R. Brain natriuretic peptide and endothelin-1 in the pathogenesis of polyhydramnios-oligohydramnios in monochorionic twins. Am J Obstet Gynecol 2003;189:189-94.

(16.) The puerperium. In: Cunningham FG, Gant NF, Leveno KJ, Gilstrap LC, Hauth JC, Wenstrom KID, eds. Williams obstetrics, 21st ed. New York: McGraw-Hill, 2001:403-22.

(17.) Jankowski M, Wang D, Mukaddam-Daher S, Gutkowska J. Pregnancy alters nitric oxide synthase and natriuretic peptide systems in the rat left ventricle. J Endocrinol 2005;184:209-17.

(18.) Ueland K, Metcalfe J. Circulatory changes in pregnancy. Clin Obstet Gynecol 1975;18:41-50.

Ahinoam Lev-Sagie [1]

Benjamin Bar-Oz [2]

Lea Salpeter [3]

Drorith Hochner-Celnikier [1]

Ilan Arad [2]

Amiram Nir [4]

Departments of [1] Obstetrics and Gynecology [2] Neonatology, and [3] Clinical Biochemistry and the [4] Pediatric Cardiology Unit Hadassah-Hebrew University Medical Center Jerusalem, Israel

* Address correspondence to this author at: Department of Obstetrics and Gynecology, Hadassah Mt. Scopus Hospital, PO Box 24035, Jerusalem 91240, Israel. Fax 972-2-5814210; e-mail levsagie@netvision.net.il.

DOI: 10.1373/clinchem.2005.054023
COPYRIGHT 2005 American Association for Clinical Chemistry, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2005 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:Letters
Author:Lev-Sagie, Ahinoam,; Bar-Oz, Benjamin; Hochner-Celnikier, Drorith; Arad, Ilan; Nir, Amiram
Publication:Clinical Chemistry
Article Type:Letter to the editor
Date:Oct 1, 2005
Words:1604
Previous Article:Pseudocholinesterase activity in organophosphate poisoning after storage of unseparated blood samples at room temperature for 3 weeks.
Next Article:Clia Final Rules for Quality Systems: Quality Assessment Issues and Answers.
Topics:


Related Articles
The role of adrenomedullin and brain natriuretic peptide levels in acute rheumatic fever in adults/Eriskin akut romatizmal atesli hastalarda...
Mismeasure of C-type natriuretic peptide.
Relationship between gestational diabetes mellitus and type 2 diabetes: evidence of mitochondrial dysfunction.
Natriuretic Peptides: The Hormones of the Heart.
N-Terminal pro-B-type natriuretic peptide and echocardiographic abnormalities in severely obese patients: correlation with visceral fat.
Endocrine paradox in heart failure: resistance to biological effects of cardiac natriuretic hormones.
Reference change values for brain natriuretic peptides revisited.
Effect of different sample types and stability after blood collection of N-terminal pro-B-type natriuretic peptide as measured with Roche Elecsys...
Stability of N-terminal pro-brain natriuretic peptide after storage frozen for one year and after multiple freeze-thaw cycles.
Plasma N-terminal pro-B-type natriuretic peptide concentrations in a control population of infants and children.

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters