title: Evidence for complement activation in the amniotic fluid of women with spontaneous preterm labor and intra-amniotic infection.
abstract: OBJECTIVE
  The complement system plays an important role in host defense against infection. Concentrations of complement split products or anaphylatoxins (C3a, C4a, and C5a) in biological fluids are considered to reflect complement activation. The purpose of this study was to determine if term and preterm parturition are associated with evidence of complement activation in the amniotic fluid.
  
  
  METHODS
  Amniotic fluid (AF) samples were collected from 270 women in the following groups: (1) normal pregnant women in midtrimester (n = 70), (2) term not in labor (n = 23), (3) term in labor (n = 48), and (4) preterm labor (PTL) (n = 129). PTL was categorized into: (a) PTL without microbial invasion of the amniotic cavity (MIAC) who delivered at term (n = 42), (b) PTL who delivered preterm without MIAC (n = 57), and (c) PTL with MIAC (n = 30). C5a, C4a, and C3a concentrations in amniotic fluid were determined by ELISA. Nonparametric tests were used for statistical analysis.
  
  
  RESULTS
  (1) The median AF C5a concentration was higher in women at term than that of those in the midtrimester (p = 0.02); (2) Spontaneous labor at term was not associated with changes in AF concentrations of anaphylatoxins C3a, C4a, and C5a (all p > 0.05); (3) Among patients with PTL who delivered preterm, those with MIAC had higher AF C4a and C5a concentrations than those without infection (p < 0.01); and (4) AF C3a, C4a, and C5a concentrations were higher in patients with PTL with MIAC than in those with PTL without MIAC who delivered at term.
  
  
  CONCLUSIONS
  Patients with spontaneous preterm labor and intact membranes with microbial invasion of the amniotic cavity had higher median amniotic fluid concentration of complement split products C3a, C4a, and C5a than patients without intra-amniotic infection. These findings suggest that preterm labor in the context of infection is associated with activation of the complement system.
authors.affiliation: Perinatology Research Branch, NICHD/NIH/DHHS, Hutzel Women's Hospital, Bethesda, Maryland, USA.
authors.forename: Eleazar
authors.initials: E
authors.lastname: Soto
authors.forename: Roberto
authors.initials: R
authors.lastname: Romero
authors.forename: Karina
authors.initials: K
authors.lastname: Richani
authors.forename: Bo H
authors.initials: BH
authors.lastname: Yoon
authors.forename: Tinnakorn
authors.initials: T
authors.lastname: Chaiworapongsa
authors.forename: Edi
authors.initials: E
authors.lastname: Vaisbuch
authors.forename: Pooja
authors.initials: P
authors.lastname: Mittal
authors.forename: Offer
authors.initials: O
authors.lastname: Erez
authors.forename: Francesca
authors.initials: F
authors.lastname: Gotsch
authors.forename: Moshe
authors.initials: M
authors.lastname: Mazor
authors.forename: Juan P
authors.initials: JP
authors.lastname: Kusanovic
mesh_terms: D000328:Adult; D000649:Amniocentesis; D000653:Amniotic Fluid / Q000378:metabolism*; D002821:Chorioamnionitis / Q000378:metabolism*; D003165:Complement System Proteins / Q000378:metabolism*; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007752:Obstetric Labor, Premature / Q000378:metabolism*; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D047929:Term Birth / Q000378:metabolism
chemical_list: D003165:Complement System Proteins