title: Exploration and confirmation of factors associated with uncomplicated pregnancy in nulliparous women: prospective cohort study.
abstract: OBJECTIVE
  To identify factors at 15 and 20 weeks' gestation associated with a subsequent uncomplicated pregnancy.
  
  
  METHODS
  Prospective international multicentre observational cohort study.
  
  
  METHODS
  Auckland, New Zealand and Adelaide, Australia (exploration and local replication dataset) and Manchester, Leeds, and London, United Kingdom, and Cork, Republic of Ireland (external confirmation dataset).
  
  
  METHODS
  5628 healthy nulliparous women with a singleton pregnancy.
  
  
  METHODS
  Uncomplicated pregnancy, defined as a normotensive pregnancy delivered at >37 weeks' gestation, resulting in a liveborn baby not small for gestational age, and the absence of any other significant pregnancy complications. In a stepwise logistic regression the comparison group was women with a complicated pregnancy.
  
  
  RESULTS
  Of the 5628 women, 3452 (61.3%) had an uncomplicated pregnancy. Factors that reduced the likelihood of an uncomplicated pregnancy included increased body mass index (relative risk 0.74, 95% confidence intervals 0.65 to 0.84), misuse of drugs in the first trimester (0.90, 0.84 to 0.97), mean diastolic blood pressure (for each 5 mm Hg increase 0.92, 0.91 to 0.94), and mean systolic blood pressure (for each 5 mm Hg increase 0.95, 0.94 to 0.96). Beneficial factors were prepregnancy fruit intake at least three times daily (1.09, 1.01 to 1.18) and being in paid employment (per eight hours' increase 1.02, 1.01 to 1.04). Detrimental factors not amenable to alteration were a history of hypertension while using oral contraception, socioeconomic index, family history of any hypertensive complications in pregnancy, vaginal bleeding during pregnancy, and increasing uterine artery resistance index. Smoking in pregnancy was noted to be a detrimental factor in the initial two datasets but did not remain in the final model.
  
  
  CONCLUSIONS
  This study identified factors associated with normal pregnancy through adoption of a novel hypothesis generating approach, which has shifted the emphasis away from adverse outcomes towards uncomplicated pregnancies. Although confirmation in other cohorts is necessary, this study implies that individually targeted lifestyle interventions (normalising maternal weight, increasing prepregnancy fruit intake, reducing blood pressure, stopping misuse of drugs) may increase the likelihood of normal pregnancy outcomes.
  
  
  BACKGROUND
  Australian New Zealand Clinical Trials Registry ACTRN12607000551493.
authors.affiliation: Division of Women's Health, Women's Health Academic Centre, King's College London and King's Health Partners, UK.
authors.forename: Lucy C
authors.initials: LC
authors.lastname: Chappell
authors.forename: Paul T
authors.initials: PT
authors.lastname: Seed
authors.forename: Jenny
authors.initials: J
authors.lastname: Myers
authors.forename: Rennae S
authors.initials: RS
authors.lastname: Taylor
authors.forename: Louise C
authors.initials: LC
authors.lastname: Kenny
authors.forename: Gustaaf A
authors.initials: GA
authors.lastname: Dekker
authors.forename: James J
authors.initials: JJ
authors.lastname: Walker
authors.forename: Lesley M E
authors.initials: LM
authors.lastname: McCowan
authors.forename: Robyn A
authors.initials: RA
authors.lastname: North
authors.forename: Lucilla
authors.initials: L
authors.lastname: Poston
mesh_terms: D000328:Adult; D001315:Australia / Q000453:epidemiology; D001794:Blood Pressure; D015992:Body Mass Index; D015331:Cohort Studies; D004032:Diet; D004651:Employment / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D006973:Hypertension / Q000453:epidemiology; D007494:Ireland / Q000453:epidemiology; D016015:Logistic Models; D009520:New Zealand / Q000453:epidemiology; D010298:Parity; D011247:Pregnancy / Q000706:statistics & numerical data; D011248:Pregnancy Complications / Q000453:epidemiology*; D011249:Pregnancy Complications, Cardiovascular / Q000453:epidemiology; D011256:Pregnancy Outcome; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology; D012959:Socioeconomic Factors; D006113:United Kingdom / Q000453:epidemiology; D055988:Uterine Artery / Q000503:physiopathology; D014652:Vascular Diseases / Q000453:epidemiology; D014655:Vascular Resistance / Q000502:physiology; D055815:Young Adult