title: Asthma in Swedish children conceived by in vitro fertilisation.
abstract: OBJECTIVE
  To investigate a proposed association between in vitro fertilisation (IVF) and child asthma.
  
  
  METHODS
  The risk for asthma after IVF was estimated as ORs using Mantel-Haenszel analysis.
  
  
  METHODS
  The Swedish Medical Birth Register.
  
  
  METHODS
  Of the 2 628 728 children born in 1982-2007 and surviving the perinatal period, 31 918 were conceived by IVF. Presence of asthma was defined as at least five prescriptions of antiasthmatic drugs during the period 1 July 2005-31 December 2009 according to the Swedish Prescribed Drug Register (115 767 children, 2323 of whom were born after IVF).
  
  
  RESULTS
  A significantly increased risk for asthma, albeit small, was found in children conceived by IVF (aOR 1.28, 95% CI 1.23 to 1.34), increasing the absolute risk from 4.4% to 5.6%. The risk increase for asthma was the same in boys and girls, in singletons and twins, and after caesarean section and vaginal delivery. The risk was higher for preterm than term singletons. For children with a low Apgar score, respiratory diagnoses, mechanical ventilation, continuous positive airway pressure or neonatal sepsis, the effect of IVF on asthma risk was low and statistically non-significant. Adjustment for length of involuntary childlessness eliminated the effect, and removal of infants whose mothers had used antiasthmatics in early pregnancy reduced the risk.
  
  
  CONCLUSIONS
  This study verifies an association between IVF and asthma in children. This can be partly explained by neonatal morbidity and by maternal asthma acting as mediators, but the main risk factor is parental subfertility. The mechanism for this is unclear.
authors.affiliation: Tornblad Institute, Lund University, Biskopsgatan 7, Lund SE-223 62, Sweden. Bengt.Kallen@med.lu.se
authors.forename: Bengt
authors.initials: B
authors.lastname: Källén
authors.forename: Orvar
authors.initials: O
authors.lastname: Finnström
authors.forename: Karl-Gösta
authors.initials: KG
authors.lastname: Nygren
authors.forename: Petra
authors.initials: P
authors.lastname: Otterblad Olausson
mesh_terms: D018927:Anti-Asthmatic Agents / Q000627:therapeutic use*; D001249:Asthma / Q000209:etiology* / Q000628:therapy; D002648:Child; D002675:Child, Preschool; D036861:Delivery, Obstetric; D005260:Female; D005307:Fertilization in Vitro / Q000009:adverse effects*; D006801:Humans; D016014:Linear Models; D008297:Male; D008423:Maternal Age; D012307:Risk Factors; D013548:Sweden
chemical_list: D018927:Anti-Asthmatic Agents