Asthma in Swedish children conceived by in vitro fertilisation
- 1Tornblad Institute, University of Lund, Lund, Sweden
- 2Department of Paediatrics, University Hospital, Linköping, Sweden
- 3Department of Medical Epidemiology and Biostatistics, Karolinska Institute, Stockholm, Sweden
- 4Department of Statistics, Monitoring and Analyses, National Board of Health and Welfare, Stockholm, Sweden
- Correspondence to Professor Bengt Källén, Tornblad Institute, Lund University, Biskopsgatan 7, Lund SE-223 62, Sweden;
- Received 3 February 2012
- Revised 26 June 2012
- Accepted 28 June 2012
- Published Online First 8 August 2012
Objectives To investigate a proposed association between in vitro fertilisation (IVF) and child asthma.
Design The risk for asthma after IVF was estimated as ORs using Mantel–Haenszel analysis.
Setting The Swedish Medical Birth Register.
Patients 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.