title: Risk factors for preterm birth in an international prospective cohort of nulliparous women.
abstract: OBJECTIVE
  To identify risk factors for spontaneous preterm birth (birth <37 weeks gestation) with intact membranes (SPTB-IM) and SPTB after prelabour rupture of the membranes (SPTB-PPROM) for nulliparous pregnant women.
  
  
  METHODS
  Prospective international multicentre cohort.
  
  
  METHODS
  3234 healthy nulliparous women with a singleton pregnancy, follow up was complete in 3184 of participants (98.5%).
  
  
  RESULTS
  Of the 3184 women, 156 (4.9%) had their pregnancy complicated by SPTB; 96 (3.0%) and 60 (1.9%) in the SPTB-IM and SPTB-PPROM categories, respectively. Independent risk factors for SPTB-IM were shorter cervical length, abnormal uterine Doppler flow, use of marijuana pre-pregnancy, lack of overall feeling of well being, being of Caucasian ethnicity, having a mother with diabetes and/or a history of preeclampsia, and a family history of low birth weight babies. Independent risk factors for SPTB-PPROM were shorter cervical length, short stature, participant's not being the first born in the family, longer time to conceive, not waking up at night, hormonal fertility treatment (excluding clomiphene), mild hypertension, family history of recurrent gestational diabetes, and maternal family history of any miscarriage (risk reduction). Low BMI (<20) nearly doubled the risk for SPTB-PPROM (odds ratio 2.64; 95% CI 1.07-6.51). The area under the receiver operating characteristics curve (AUC), after internal validation, was 0.69 for SPTB-IM and 0.79 for SPTB-PPROM.
  
  
  CONCLUSIONS
  The ability to predict PTB in healthy nulliparous women using clinical characteristics is modest. The dissimilarity of risk factors for SPTB-IM compared with SPTB-PPROM indicates different pathophysiological pathways underlie these distinct phenotypes.
  
  
  BACKGROUND
  ACTR.org.au ACTRN12607000551493.
authors: Lyell McEwin Hospital, Adelaide, South Australia, Australia. gustaaf.dekker@adelaide.edu.au
authors: Gustaaf Albert
authors: GA
authors: Dekker
authors: Shalem Y
authors: SY
authors: Lee
authors: Robyn A
authors: RA
authors: North
authors: Lesley M
authors: LM
authors: McCowan
authors: Nigel A B
authors: NA
authors: Simpson
authors: Claire T
authors: CT
authors: Roberts
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement; D015331:Cohort Studies; D023381:Endpoint Determination; D005260:Female; D006801:Humans; D038622:Internationality; D015233:Models, Statistical; D015999:Multivariate Analysis; D010298:Parity; D011247:Pregnancy; D047928:Premature Birth / Q000000981:diagnostic imaging / Q000453:epidemiology*; D011446:Prospective Studies; D012307:Risk Factors