title: Hormonal contraceptive use before and after conception in relation to preterm birth and small for gestational age: an observational cohort study.
abstract: OBJECTIVE
  To evaluate whether hormonal contraceptives, used before or in early pregnancy, confer increased risk of preterm birth or reduced fetal growth.
  
  
  METHODS
  Population-based cohort study conducted by the Norwegian Institute of Public Health (Mother and Child Cohort Study, 1998-2008) with linkage to the Norwegian Prescription Registry and to the Medical Birth Registry of Norway.
  
  
  METHODS
  Norway.
  
  
  METHODS
  Of the 48,615 pregnancies meeting study inclusion criteria, 44,734 pregnancies were included in the complete case analysis.
  
  
  METHODS
  We characterised hormonal contraception by type (combination oral, progestin-only oral, vaginal ring, transdermal, and injectable) and specific progestin component. We used generalised estimating equations to estimate the odds of adverse outcome according to formulation used. Several sensitivity analyses were conducted.
  
  
  METHODS
  Preterm birth, small for gestational age.
  
  
  RESULTS
  We observed a positive association between use of a combination oral contraceptive and preterm birth for all exposure periods (e.g. adjusted odds ratio 1.21, 95% confidence interval 1.04-1.41 for last use 12 to >4 months before conception); combination contraceptives containing the progestin norethisterone were consistently related to risk. Other types of hormonal contraception were generally not associated with preterm birth; none were related to small for gestational age. Observed associations were robust to sensitivity analyses.
  
  
  CONCLUSIONS
  Hormonally active agents may exert dose-, agent-, and timing-specific effects on growth and development. We found that the particular progestin component is important when assessing the potential for adverse effects among former users of hormonal contraceptives.
authors.affiliation: National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA.|Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: E T
authors.initials: ET
authors.lastname: Jensen
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Daniels
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: T
authors.initials: T
authors.lastname: Stürmer
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: W R
authors.initials: WR
authors.lastname: Robinson
authors.affiliation: National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Williams
authors.affiliation: National Institute of Public Health, Oslo, Norway.
authors.forename: K
authors.initials: K
authors.lastname: Vejrup
authors.affiliation: National Institute of Public Health, Oslo, Norway.
authors.forename: P
authors.initials: P
authors.lastname: Magnus
authors.affiliation: National Institutes of Health, National Institute of Environmental Health Sciences, Research Triangle Park, NC, USA.
authors.forename: M P
authors.initials: MP
authors.lastname: Longnecker
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D003271:Contraceptive Agents, Female / Q000009:adverse effects*; D003278:Contraceptives, Oral, Hormonal / Q000009:adverse effects; D005260:Female; D005317:Fetal Growth Retardation / Q000139:chemically induced*; D006801:Humans; D007236:Infant, Small for Gestational Age; D008875:Middle Aged; D009664:Norway; D016017:Odds Ratio; D016742:Preconception Care; D011247:Pregnancy; D047928:Premature Birth / Q000139:chemically induced*; D011372:Progestins / Q000009:adverse effects; D012042:Registries; D012307:Risk Factors; D055815:Young Adult
chemical_list: D003271:Contraceptive Agents, Female; D003278:Contraceptives, Oral, Hormonal; D011372:Progestins
keywords: Hormonal contraceptives; Mother and child Cohort Study (MoBa); preterm birth; small for gestational age