By Kirsty Oswald, medwireNews Reporter
Researchers from Greece have shown that pediatric asthma is associated with both conception by in vitro fertilization (IVF) and birth by cesarean section.
Furthermore, they found that each risk factor may have a confounding effect on the other, which could explain why previous studies into the associations have produced conflicting results.
The team, led by Nikolaos Papadopoulos (University of Athens), analyzed data from questionnaires completed by the parents of 2016 children, of whom 59 (2.9%) were conceived by IVF, and 579 (28.7%) were born by cesarean section.
They found that both IVF and birth by cesarean section were significantly associated with the odds for asthma at age 9 to 13 years, reported by 273 (13.5%) overall. After accounting for numerous confounding factors, IVF was associated with a 2.25-fold greater odds for asthma compared with natural fertilization (28.8 vs 13.1%), and cesarean section was associated with a 1.39-fold increased odds compared with vaginal delivery (16.8 vs 12.2%).
“This supports the existence of a true IVF/[cesarean section] link with asthma,” comment the authors.
However, when they combined IVF and cesarean section within the same model, they found that the correlations with asthma were weakened.
“This suggests that either variable could exert a confounding effect on the other, a notion that is not surprising in light of the increased probability of IVF offspring to be delivered through [cesarean section],” say Papadopoulos and team. They note though that both factors remained significantly associated with asthma, indicating a likely independent association.
Writing in Clinical & Experimental Allergy, the authors explain that while several large studies have reported associations between cesarean section and asthma, reports have been inconsistent, with some investigators failing to replicate the finding. Meanwhile, “the evidence for a link of IVF with asthma is controversial and inconclusive,” they say.
They conclude that the confounding detected by their study has probably hindered previous studies and advise that it be taken into account in future research.
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