title: Infertility, infertility treatment, and congenital malformations: Danish national birth cohort.
abstract: OBJECTIVE
  To examine whether infertile couples (with a time to pregnancy of > 12 months), who conceive naturally or after treatment, give birth to children with an increased prevalence of congenital malformations.
  
  
  METHODS
  Longitudinal study.
  
  
  METHODS
  Danish national birth cohort.
  
  
  METHODS
  Three groups of liveborn children and their mothers: 50,897 singletons and 1366 twins born of fertile couples (time to pregnancy < or = 12 months), 5764 singletons and 100 twins born of infertile couples who conceived naturally (time to pregnancy > 12 months), and 4588 singletons and 1690 twins born after infertility treatment.
  
  
  METHODS
  Prevalence of congenital malformations determined from hospital discharge diagnoses.
  
  
  RESULTS
  Compared with singletons born of fertile couples, singletons born of infertile couples who conceived naturally or after treatment had a higher prevalence of congenital malformations-hazard ratios 1.20 (95% confidence interval 1.07 to 1.35) and 1.39 (1.23 to 1.57). The overall prevalence of congenital malformations increased with increasing time to pregnancy. When the analysis was restricted to singletons born of infertile couples, babies born after treatment had an increased prevalence of genital organ malformations (hazard ratio 2.32, 1.24 to 4.35) compared with babies conceived naturally. No significant differences existed in the overall prevalence of congenital malformations among twins.
  
  
  CONCLUSIONS
  Hormonal treatment for infertility may be related to the occurrence of malformations of genital organs, but our results suggest that the reported increased prevalence of congenital malformations seen in singletons born after assisted reproductive technology is partly due to the underlying infertility or its determinants. The association between untreated infertility and congenital malformations warrants further examination.
authors.affiliation: Danish Epidemiology Science Centre, Department of Epidemiology, Institute of Public Health, University of Aarhus, DK 8000 Aarhus C, Denmark. zjl@soci.au.dk
authors.forename: Jin Liang
authors.initials: JL
authors.lastname: Zhu
authors.forename: Olga
authors.initials: O
authors.lastname: Basso
authors.forename: Carsten
authors.initials: C
authors.lastname: Obel
authors.forename: Camilla
authors.initials: C
authors.lastname: Bille
authors.forename: Jørn
authors.initials: J
authors.lastname: Olsen
mesh_terms: D015331:Cohort Studies; D000013:Congenital Abnormalities / Q000453:epidemiology*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D007246:Infertility / Q000453:epidemiology / Q000628:therapy*; D008297:Male; D015995:Prevalence; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects*; D012307:Risk Factors