title: Amniotic fluid Clara cell protein concentration in normal pregnancy, a marker of fetal airway growth or fetal lung maturation?
abstract: OBJECTIVE
  To evaluate the relationship of Clara cell protein (CCP) in amniotic fluid (AF) with the lecithin/sphingomyelin (L/S) ratio, and the concentrations of saturated phosphatidylcholine (Sat PC) and surfactant protein A (SP-A).
  
  
  METHODS
  AF samples were obtained by amniocentesis from 98 pregnancies without conditions known to influence fetal lung maturation between 25 and 41 weeks of gestation. These samples were used for determinations of CCP, L/S ratio, Sat PC, and SP-A. Simple and multiple linear regressions were used to analyze the data.
  
  
  RESULTS
  CCP in AF increased logarithmically with gestational age (R(2)=0.51, p=0.006). The L/S ratio (R(2)=0.41, p<0.001), and the concentrations of Sat PC (R(2)=0.26, p<0.001) and SP-A (R(2)=0.52, p<0.001) also increased with advancing gestation. Weak correlations of CCP with the L/S ratio (R(2)=0.22, p=0.009) and Sat PC (R(2)=0.12, p=0.004), but not with SP-A (R(2)=0.07, p=0.10), were found. Using multiple linear regressions, gestational age was the only predictor of CCP (F=10.9, R(2)=0.13, p=0.015). Conversely, gestational age, Sat PC, and SP-A accounted for most of the variation of the L/S ratio (F=34.7, R(2)=0.61, p=0.0001).
  
  
  CONCLUSIONS
  CCP correlated very poorly with known and widely accepted indices of fetal lung maturation. The increasing concentration of CCP in AF throughout gestation probably reflects growth and development of the fetal airways.
authors.affiliation: Department of Pediatrics, Centro de Investigaciones Perinatales, University of Chile, Santiago, Chile.
authors.forename: A
authors.initials: A
authors.lastname: Maturana
authors.forename: A
authors.initials: A
authors.lastname: Bernard
authors.forename: A M
authors.initials: AM
authors.lastname: Germain
authors.forename: V L
authors.initials: VL
authors.lastname: Chau
authors.forename: F R
authors.initials: FR
authors.lastname: Moya
mesh_terms: D000653:Amniotic Fluid / Q000737:chemistry*; D001980:Bronchi / Q000196:embryology*; D005260:Female; D005325:Fetal Organ Maturity; D005333:Fetus / Q000502:physiology*; D005865:Gestational Age; D006801:Humans; D008168:Lung / Q000196:embryology*; D010713:Phosphatidylcholines / Q000032:analysis; D011247:Pregnancy; D011506:Proteins / Q000032:analysis*; D013109:Sphingomyelins / Q000032:analysis; D014598:Uteroglobin / Q000032:analysis*
chemical_list: D010713:Phosphatidylcholines; D011506:Proteins; C556389:SCGB1A1 protein, human; D013109:Sphingomyelins; D014598:Uteroglobin