title: Amniotic fluid prostaglandin concentrations increase before the onset of spontaneous labor at term.
abstract: OBJECTIVE
  The role of prostaglandins (PGs) in the onset of human parturition has been controversial. Specifically, some investigators have proposed that PGs are the consequence rather than the cause of labor. An important question is whether or not amniotic fluid (AF) PG concentrations increase before the onset of labor in humans.
  
  
  METHODS
  The concentrations of PGs were determined in AF obtained from 167 singleton pregnant women with intact membranes. Patients were divided into four groups: (1) preterm not in labor (gestational age 15-36 weeks, n = 65); (2) term not in labor (n = 68); (3) spontaneous labor at term with cervical dilatation < 4 cm (n = 25); (4) spontaneous labor at term with cervical dilatation > or = 4 cm (n = 9). AF was obtained by transabdominal amniocentesis or collected at the time of cesarean delivery. All patients met the following criteria: (1) normal pregnancy outcome; (2) clear AF; (3) no significant medical or obstetric complications such as diabetes mellitus, preeclampsia, preterm birth, fetal growth restriction, or major congenital malformations; and (4) no significant neonatal complications. The concentrations of PGE2 and PGF2a in AF were determined by enzyme-linked immunosorbent assay (ELISA). Non-parametric analysis was performed.
  
  
  RESULTS
  (1) AF PG concentrations remained unchanged with advancing gestation until 36 weeks of gestation; (2) however, an abrupt increase in AF PG concentrations was observed before the onset of labor at term; (3) among cases without labor at term, the median AF PGF2a concentration increased with advancing gestation; (4) the presence of labor and the degree of cervical dilatation were significantly associated with a higher concentration of PGF2a.
  
  
  CONCLUSIONS
  An abrupt increase in AF PG concentrations (25-fold for PGF2a) occurs before the onset of spontaneous labor at term in humans; these observations suggest that PGs increase prior to the onset of labor and contradict the claim that an increase in PG concentrations is the consequence of labor.
authors.affiliation: Department of Obstetrics and Gynecology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Si Eun
authors.initials: SE
authors.lastname: Lee
authors.forename: Roberto
authors.initials: R
authors.lastname: Romero
authors.forename: In-Sook
authors.initials: IS
authors.lastname: Park
authors.forename: Hyo Suk
authors.initials: HS
authors.lastname: Seong
authors.forename: Chan-Wook
authors.initials: CW
authors.lastname: Park
authors.forename: Bo Hyun
authors.initials: BH
authors.lastname: Yoon
mesh_terms: D000328:Adult; D000653:Amniotic Fluid / Q000737:chemistry*; D015237:Dinoprost / Q000032:analysis; D015232:Dinoprostone / Q000032:analysis; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005865:Gestational Age; D006801:Humans; D007745:Labor Onset / Q000378:metabolism*; D007747:Labor Stage, First; D011247:Pregnancy; D011453:Prostaglandins / Q000032:analysis*
chemical_list: D011453:Prostaglandins; D015237:Dinoprost; D015232:Dinoprostone