title: Effect of labor on postpartum clearance of cell-free fetal DNA from the maternal circulation.
abstract: OBJECTIVE
  The aim of this study was to compare the effect of mode of delivery on the postpartum clearance of cell-free fetal (cff) DNA.
  
  
  METHODS
  Women who gave birth to a single-term male infant by any mode of delivery had blood collected on three occasions: within 3 h of birth, on day 1-2 postpartum and at 2 weeks postpartum. The SRY sequence was used as a marker of cff DNA, and was detected using conventional PCR.
  
  
  RESULTS
  Eighty-seven women were included in the study. There were 28 women in the elective caesarean section group and 59 in the labor group. Cell-free fetal DNA was detected in 38/87 (44%) of women within 3 h of birth. There was a significant difference between the group that labored and the group that did not (54 vs 21%, p = 0.003). Twelve percent of women who labored had persistent cff DNA on day 1-2 postpartum, compared with none of the women who delivered without labor. No woman had DNA that persisted up to 2 weeks postpartum.
  
  
  CONCLUSIONS
  The presence of labor increases the rate of detectable DNA in women within 3 h of birth and on day 1-2 postpartum. Postpartum clearance was completed by 2 weeks in all women tested regardless of mode of delivery.
authors.affiliation: Department of Maternal Fetal Medicine, Royal Hospital for Women, Sydney, Australia. lisahui77@gmail.com
authors.forename: L
authors.initials: L
authors.lastname: Hui
authors.forename: J I
authors.initials: JI
authors.lastname: Vaughan
authors.forename: M
authors.initials: M
authors.lastname: Nelson
mesh_terms: D004247:DNA / Q000097:blood / Q000493:pharmacokinetics*; D005260:Female; D005333:Fetus / Q000378:metabolism; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007743:Labor, Obstetric / Q000378:metabolism / Q000502:physiology*; D008297:Male; D008431:Maternal-Fetal Exchange / Q000235:genetics; D008657:Metabolic Clearance Rate; D009035:Mothers; D049590:Postpartum Period / Q000097:blood* / Q000378:metabolism; D011247:Pregnancy; D013997:Time Factors
chemical_list: D004247:DNA