title: Reference intervals for N-terminal pro-B-type natriuretic peptide in amniotic fluid between 10 and 34 weeks of gestation.
abstract: BACKGROUND
  In adult and pediatric cardiology, n-terminal pro-B-type natriuretic peptide (nt-proBNP) serves as biomarker in the diagnosis and management of cardiovascular dysfunction. Elevated levels of circulating nt-proBNP are present in fetal conditions associated with myocardial pressure or volume load. Compared to fetal blood sampling, amniocentesis is technically easier and can be performed from early pregnancy onwards. We aimed to investigate amniotic fluid (AF) nt-proBNP concentrations in normal pregnancies between 10 and 34 weeks of gestation.
  
  
  METHODS
  Nt-proBNP and total protein (TP) was measured in AF by chemiluminescence assay (photometry, respectively). To adjust for a potential dilutional effect, the AF-nt-proBNP/AF-TP ratio was analyzed. Reference intervals were constructed by regression modeling across gestational age.
  
  
  RESULTS
  132 samples were analyzed. A negative correlation between AF-nt-proBNP/AF-TP ratio and gestational age was observed. Curves for the mean and the 5% and 95% reference interval between 10 and 34 weeks of gestation were established.
  
  
  CONCLUSIONS
  In normal pregnancy, nt-proBNP is present in AF and decreases during gestation. Our data provide the basis for research on AF-nt-proBNP as biomarker in fetal medicine.
authors.affiliation: Department of Obstetrics and Prenatal Medicine, University Bonn Medical School, Bonn, Germany.
authors.forename: Waltraut M
authors.initials: WM
authors.lastname: Merz
authors.affiliation: Department of Obstetrics and Prenatal Medicine, University Bonn Medical School, Bonn, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Leufgen
authors.affiliation: Institute for Medical Biometry, Informatics and Epidemiology, University Bonn Medical School, Bonn, Germany.
authors.forename: Rolf
authors.initials: R
authors.lastname: Fimmers
authors.affiliation: Institute for Clinical Chemistry and Pharmacology, University Bonn Medical School, Bonn, Germany.
authors.forename: Birgit
authors.initials: B
authors.lastname: Stoffel-Wagner
authors.affiliation: Department of Obstetrics and Prenatal Medicine, University Bonn Medical School, Bonn, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Gembruch
mesh_terms: D000293:Adolescent; D000328:Adult; D000653:Amniotic Fluid / Q000737:chemistry*; D015415:Biomarkers / Q000032:analysis; D019963:Clinical Chemistry Tests / Q000592:standards*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020097:Natriuretic Peptide, Brain / Q000032:analysis*; D010446:Peptide Fragments / Q000032:analysis*; D011247:Pregnancy; D012016:Reference Values; D055815:Young Adult
chemical_list: D015415:Biomarkers; D010446:Peptide Fragments; C109794:pro-brain natriuretic peptide (1-76); D020097:Natriuretic Peptide, Brain