title: Quantitative Fetal Fibronectin at 18 Weeks of Gestation to Predict Preterm Birth in Asymptomatic High-Risk Women.
abstract: OBJECTIVE
  To compare quantitative fetal fibronectin measurement from 18 to 21 weeks of gestation to measurement at 22-27 weeks of gestation for the prediction of spontaneous preterm birth.
  
  
  METHODS
  In a prospective cohort study, we studied the accuracy of cervicovaginal fluid quantitative fetal fibronectin concentrations measured between 18 0/7 weeks of gestation and 21 6/7 weeks of gestation in high-risk asymptomatic women to predict spontaneous preterm birth before 34 weeks of gestation. Predefined fibronectin thresholds were 10 or greater, 50 or greater, and 200 ng/mL or greater. Diagnostic accuracy of the early test (n=898) was compared with the standard test performed between 22 0/7 and 27 6/7 weeks of gestation (n=691) in the same cohort. Subgroup analysis was performed according to cervical length measurement.
  
  
  RESULTS
  Of 898 women, 8.7% delivered spontaneously before 34 weeks of gestation. Only 3.8% of the women with concentrations less than 10 ng/mL (65% of test results) delivered before 34 weeks of gestation. A concentration threshold of 10 ng/mL measured at 18 and 22 weeks of gestation had comparably high sensitivity (early 0.71, 95% confidence interval 0.60-0.81; standard 0.76, 0.63-0.87) and negative predictive value (early 0.96, 0.94-0.98; standard 0.97, 0.95-0.99) for delivery before 34 weeks of gestation. Specificity was also comparable (early 0.69, 0.65-0.72; standard 0.70, 0.66-0.74). A threshold of 200 ng/mL had high specificity (early 0.96, 0.94-0.98; standard 0.96, 0.94-0.97) with lower sensitivity (early 0.26, 0.17-0.37; standard 0.35, 0.22-0.49). Consideration of cervical length strengthened prediction.
  
  
  CONCLUSIONS
  Quantitative cervicovaginal fetal fibronectin measured from 18 to 21 weeks of gestation has similar predictive value as measurement at 22-27 weeks of gestation for prediction of spontaneous preterm birth. Low fibronectin concentrations are associated with spontaneous preterm birthrates approaching population background levels.
authors.affiliation: Division of Women's Health, King's College London, Women's Health Academic Centre, Kings Health Partners, London, and the Department of Obstetrics and Gynaecology, West Middlesex Hospital, Middlesex, United Kingdom; and Monash School of Medicine, Melbourne, Australia.
authors.forename: Natasha L
authors.initials: NL
authors.lastname: Hezelgrave
authors.forename: Danielle S
authors.initials: DS
authors.lastname: Abbott
authors.forename: Samara K
authors.initials: SK
authors.lastname: Radford
authors.forename: Paul T
authors.initials: PT
authors.lastname: Seed
authors.forename: Joanna C
authors.initials: JC
authors.lastname: Girling
authors.forename: Judy
authors.initials: J
authors.lastname: Filmer
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Tribe
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Shennan
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement; D005260:Female; D005353:Fibronectins / Q000032:analysis*; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011262:Pregnancy Trimester, Second; D047928:Premature Birth / Q000175:diagnosis*; D011446:Prospective Studies; D014626:Vaginal Smears
chemical_list: C403421:FFN protein, human; D005353:Fibronectins