title: Risk factors for preterm delivery: do they add to fetal fibronectin testing and cervical length measurement in the prediction of preterm delivery in symptomatic women?
abstract: OBJECTIVE
  To assess whether patient characteristics add to the fetal fibronectin test and cervical length measurement in the prediction of preterm delivery in symptomatic women.
  
  
  METHODS
  A nationwide prospective cohort study was conducted in all ten perinatal centres in the Netherlands. Women with symptoms of preterm labour between 24 and 34 weeks gestation with intact membranes were invited. In all women qualitative fibronectin testing (0.050 μg/mL cut-off) and cervical length measurement were performed. Only singleton pregnancies were included in this analysis. Logistic regression was used to construct two multivariable models to predict spontaneously delivery within 7 days: a model including cervical length and fetal fibronectin as predictors, and an extended model including all potential predictors. The models were internally validated using bootstrapping techniques. Predictive performances were assessed as the area under the receiver operator characteristic curve (AUC) and calibration plots. We compared the models' capability to identify women with a low risk to deliver within 7 days. A risk less than 5%, corresponding to the risk for women with a cervical length of at least 25 mm, was considered as low risk.
  
  
  RESULTS
  Seventy-three of 600 included women (12%) had delivered spontaneously within 7 days. The extended model included maternal age, parity, previous preterm delivery, vaginal bleeding, C-reactive protein, cervical length, dilatation and fibronectin status. Both models had high discriminative performances (AUC of 0.92 (95% CI 0.88-0.95) and 0.95 (95% CI 0.92-0.97) respectively). Compared to the model with fibronectin and cervical length, our extended model reclassified 38 women (6%) from low risk to high risk and 21 women (4%) from high risk to low risk. Preterm delivery within 7 days occurred once in both the reclassification groups.
  
  
  CONCLUSIONS
  In women with symptoms of preterm labour before 34 weeks gestation, a model that integrates maternal characteristics, clinical signs and laboratory tests, did not predict delivery within 7 days better than a model with only fibronectin and cervical length.
authors.affiliation: Department of Obstetrics and Gynaecology, Academic Medical Centre, Amsterdam, Netherlands. Electronic address: g.j.vanbaaren@amc.uva.nl.
authors.forename: Gert-Jan
authors.initials: GJ
authors.lastname: van Baaren
authors.affiliation: Department of Obstetrics and Gynaecology, Academic Medical Centre, Amsterdam, Netherlands.
authors.forename: Merel M C
authors.initials: MM
authors.lastname: Bruijn
authors.affiliation: Department of Clinical Chemistry and Haematology, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Jolande Y
authors.initials: JY
authors.lastname: Vis
authors.affiliation: Department of Obstetrics and Gynaecology, Catharina Hospital, Eindhoven, Netherlands.
authors.forename: Femke F
authors.initials: FF
authors.lastname: Wilms
authors.affiliation: Department of Obstetrics and Gynaecology, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Martijn A
authors.initials: MA
authors.lastname: Oudijk
authors.affiliation: Department of Obstetrics and Gynaecology, University Medical Centre Utrecht, Utrecht, Netherlands.
authors.forename: Anneke
authors.initials: A
authors.lastname: Kwee
authors.affiliation: Department of Obstetrics and Gynaecology, Máxima Medical Centre, Veldhoven, Netherlands.
authors.forename: Martina M
authors.initials: MM
authors.lastname: Porath
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital Maastricht, Maastricht, Netherlands.
authors.forename: Guid
authors.initials: G
authors.lastname: Oei
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital Maastricht, Maastricht, Netherlands.
authors.forename: Hubertina C J
authors.initials: HC
authors.lastname: Scheepers
authors.affiliation: Department of Obstetrics and Gynaecology, University Hospital Maastricht, Maastricht, Netherlands.
authors.forename: Marc E A
authors.initials: ME
authors.lastname: Spaanderman
authors.affiliation: Department of Obstetrics, Leiden University Medical Centre, Leiden, Netherlands.
authors.forename: Kitty W M
authors.initials: KW
authors.lastname: Bloemenkamp
authors.affiliation: Department of Obstetrics, Leiden University Medical Centre, Leiden, Netherlands.
authors.forename: Monique C
authors.initials: MC
authors.lastname: Haak
authors.affiliation: Department of Obstetrics and Gynaecology, VU University Medical Centre, Amsterdam, Netherlands.
authors.forename: Antoinette C
authors.initials: AC
authors.lastname: Bolte
authors.affiliation: Department of Obstetrics and Gynaecology, VU University Medical Centre, Amsterdam, Netherlands.
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Bax
authors.affiliation: Department of Obstetrics and Gynaecology, Erasmus Medical Centre, Rotterdam, Netherlands.
authors.forename: Jérôme M J
authors.initials: JM
authors.lastname: Cornette
authors.affiliation: Department of Obstetrics and Gynaecology, Erasmus Medical Centre, Rotterdam, Netherlands.
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: Duvekot
authors.affiliation: Department of Obstetrics and Gynaecology, Isala Clinics, Zwolle, Netherlands.
authors.forename: Bas W A
authors.initials: BW
authors.lastname: Nij Bijvanck
authors.affiliation: Department of Obstetrics and Gynaecology, Isala Clinics, Zwolle, Netherlands.
authors.forename: Jim
authors.initials: J
authors.lastname: van Eijck
authors.affiliation: Department of Obstetrics and Gynaecology, University Medical Centre Groningen, Groningen, Netherlands.
authors.forename: Maureen T M
authors.initials: MT
authors.lastname: Franssen
authors.affiliation: Department of Obstetrics and Gynaecology, University Medical Centre Groningen, Groningen, Netherlands.
authors.forename: Krystyna M
authors.initials: KM
authors.lastname: Sollie
authors.affiliation: Department of Obstetrics and Gynaecology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands.
authors.forename: Frank P H A
authors.initials: FP
authors.lastname: Vandenbussche
authors.affiliation: Department of Obstetrics and Gynaecology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherlands.
authors.forename: Mallory
authors.initials: M
authors.lastname: Woiski
authors.affiliation: Department of Clinical Epidemiology, Biostatistics and Bioinformatics, Academic Medical Centre, Amsterdam, Netherlands.
authors.forename: Patrick M M
authors.initials: PM
authors.lastname: Bossuyt
authors.affiliation: Clinical Research Unit, Academic Medical Centre, Amsterdam, Netherlands.
authors.forename: Brent C
authors.initials: BC
authors.lastname: Opmeer
authors.affiliation: Department of Obstetrics and Gynaecology, The Robinson Institute, School of Paediatrics and Reproductive Health, University of Adelaide, Australia.
authors.forename: Ben W J
authors.initials: BW
authors.lastname: Mol
mesh_terms: D000328:Adult; D019540:Area Under Curve; D002097:C-Reactive Protein / Q000378:metabolism; D054791:Cervical Length Measurement; D036861:Delivery, Obstetric; D005260:Female; D005353:Fibronectins / Q000032:analysis*; D005865:Gestational Age; D006801:Humans; D007747:Labor Stage, First / Q000502:physiology; D016015:Logistic Models; D008423:Maternal Age; D015999:Multivariate Analysis; D009426:Netherlands / Q000453:epidemiology; D010298:Parity; D011237:Predictive Value of Tests; D011247:Pregnancy; D047928:Premature Birth / Q000453:epidemiology*; D011446:Prospective Studies; D012372:ROC Curve; D012008:Recurrence; D018570:Risk Assessment / Q000379:methods / Q000706:statistics & numerical data; D012307:Risk Factors; D063189:Symptom Assessment; D013997:Time Factors; D014592:Uterine Hemorrhage / Q000453:epidemiology; D055815:Young Adult
chemical_list: D005353:Fibronectins; D002097:C-Reactive Protein
keywords: Cervical length; Fetal fibronectin; Prediction; Pregnancy; Preterm labour