title: Effects of technology or maternal factors on perinatal outcome after assisted fertilisation: a population-based cohort study.
abstract: BACKGROUND
  Research suggests that singleton births following assisted fertilisation are associated with adverse outcomes; however, these results might be confounded by factors that affect both fertility and pregnancy outcome. We therefore compared pregnancy outcomes in women who had singleton pregnancies conceived both spontaneously and after assisted fertilisation.
  
  
  METHODS
  In a population-based cohort study, we assessed differences in birthweight, gestational age, and odds ratios (OR) of small for gestational age babies, premature births, and perinatal deaths in singletons (gestation >/=22 weeks or birthweight >/=500 g) born to 2546 Norwegian women (>20 years) who had conceived at least one child spontaneously and another after assisted fertilisation among 1 200 922 births after spontaneous conception and 8229 after assisted fertilisation.
  
  
  RESULTS
  In the whole study population, assisted-fertilisation conceptions were associated with lower mean birthweight (difference 25 g, 95% CI 14 to 35), shorter duration of gestation (2.0 days, 1.6 to 2.3) and increased risks of small for gestational age (OR 1.26, 1.10 to 1.44), and perinatal death (1.31, 1.05 to 1.65) than were spontaneous conceptions. In the sibling-relationship comparisons, the spontaneous versus the assisted-fertilisation conceptions showed a difference of only 9 g (-18 to 36) in birthweight and 0.6 days (-0.5 to 1.7) in gestational age. For assisted fertilisation versus spontaneous conception in the sibling-relationship comparisons, the OR for small for gestational age was 0.99 (0.62 to 1.57) and that for perinatal mortality was 0.36 (0.20 to 0.67).
  
  
  CONCLUSIONS
  Birthweight, gestational age, and risks of small for gestational age babies, and preterm delivery did not differ among infants of women who had conceived both spontaneously and after assisted fertilisation. The adverse outcomes of assisted fertilisation that we noted compared with those in the general population could therefore be attributable to the factors leading to infertility, rather than to factors related to the reproductive technology.
authors.affiliation: IVF Unit, Department of Obstetrics and Gynaecology, St Olavs University Hospital, Trondheim, Norway.
authors.forename: Liv Bente
authors.initials: LB
authors.lastname: Romundstad
authors.forename: Pål R
authors.initials: PR
authors.lastname: Romundstad
authors.forename: Arne
authors.initials: A
authors.lastname: Sunde
authors.forename: Vidar
authors.initials: V
authors.lastname: von Düring
authors.forename: Rolv
authors.initials: R
authors.lastname: Skjaerven
authors.forename: David
authors.initials: D
authors.lastname: Gunnell
authors.forename: Lars J
authors.initials: LJ
authors.lastname: Vatten
mesh_terms: D000328:Adult; D001724:Birth Weight; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D006801:Humans; D016014:Linear Models; D008429:Maternal Welfare; D009664:Norway; D010298:Parity; D011247:Pregnancy; D011256:Pregnancy Outcome; D012042:Registries; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects*