Caesarean delivery and risk of atopy and allergic disesase: meta-analyses
Article first published online: 11 FEB 2008
© 2008 The Authors; Journal compilation © 2008 Blackwell Publishing Ltd
Clinical & Experimental Allergy
Volume 38, Issue 4, pages 634–642, April 2008
How to Cite
Bager, P., Wohlfahrt, J. and Westergaard, T. (2008), Caesarean delivery and risk of atopy and allergic disesase: meta-analyses. Clinical & Experimental Allergy, 38: 634–642. doi: 10.1111/j.1365-2222.2008.02939.x
- Issue published online: 11 FEB 2008
- Article first published online: 11 FEB 2008
- Submitted 9 October 2006; revised 13 November 2007; accepted 27 November 2007
- allergic disease;
- caesarean section;
- mode of delivery;
- risk factors
Background Studies of delivery by caesarean section (c-section) and the offspring's risk of allergic diseases are of current interest due to concerns about the increased use of c-section in many countries. However, previous studies have reported inconsistent findings.
Objective We investigated whether delivery by c-section is associated with an increased risk of atopy and allergic disease by reviewing the literature, performing a meta-analysis, and assessing publication bias.
Methods We used a systematic literature search of MEDLINE (1966 to May 2007). Six common allergic outcomes were included: food allergy/food atopy, inhalant atopy, eczema/atopic dermatitis, allergic rhinitis, asthma, and hospitalization for asthma. For each outcome a meta-analysis was performed, where a summary odds ratio (OR) was calculated taking into account heterogeneity between the study-specific relative risks. Publication bias was assessed using the funnel plot method.
Results We identified 26 studies on delivery by c-section and one or more of the six allergic outcomes. C-section was associated with an increased summary OR of food allergy/food atopy (OR 1.32, 95% CI 1.12–1.55; six studies), allergic rhinitis (OR 1.23, 95% CI 1.12–1.35; seven studies), asthma (OR 1.18, 95% CI 1.05–1.32; 13 studies), and hospitalization for asthma (OR 1.21, 95% CI 1.12–1.31; seven studies), whereas there was no association with inhalant atopy (OR 1.06, 95% CI 0.82–1.38; four studies) and eczema/atopic dermatitis (OR 1.03, 95% CI 0.98–1.09; six studies). Funnel plots indicated that the association with food allergy/food atopy could be difficult to interpret due to publication bias. For each significant association with an allergic outcome, only 1–4% of cases were attributable to c-section.
Conclusion Delivery by c-section is associated with a moderate risk increase for allergic rhinitis, asthma, hospitalization for asthma, and perhaps food allergy/food atopy, but not with inhalant atopy or atopic dermatitis. The increased use of c-section during the last decades is unlikely to have contributed much to the allergy epidemic observed during the same period.