Forceps delivery ‘does not increase atopy risk’

By Mark Cowen, Senior medwireNews Reporter

Results from a population-based cohort study suggest that forceps-assisted birth is associated with an increased risk for asthma, but not allergic sensitization, in later childhood.

Robert Hancox (University of Otago, Dunedin, New Zealand) and team found that delivery with forceps assistance is associated with an increased risk for asthma at the age of 13 years, but not at 32 years, after adjustment for multiple confounding factors.

The risk for atopy following forceps-assisted birth was not significant at either age after adjustment for confounders.

Furthermore, there were no significant differences in prevalence rates of atopy and asthma at 13 and 32 years of age between individuals delivered by cesarean section and those delivered vaginally without forceps.

"The findings suggest that the previously reported associations between caesarean birth and allergic sensitisation may be due to either confounding or stress at the time of birth rather than the lack of exposure to maternal vaginal flora influencing immune development," comment the researchers in Clinical and Experimental Allergy.

The team assessed follow-up data on 1037 individuals (52% male), born in 1972 or 1973, who participated in the Dunedin Multidisciplinary Health and Development Study. Of these, 21% had a forceps-assisted birth, and 4.6% were delivered by cesarean section.

Analysis revealed that individuals delivered with forceps assistance had a higher prevalence of atopy at the ages 13 and 32 years than those born vaginally without forceps, at 53.3% versus 43.6%, and 68.1% versus 58.6%, respectively.

Participants with a forceps-assisted birth also had a higher prevalence of asthma at 13 and 32 years than those born by vaginal delivery without forceps, at 20.9% versus 11.0%, and 22.7% versus 15.9%, respectively.

There were no differences in the prevalence of atopy and asthma at 13 and 32 years of age between individuals delivered by cesarean section and those with a vaginal delivery without forceps.

In multivariate analysis, which accounted for factors such as gender, parental atopy, and socio-economic status, the risk for asthma associated with forceps-assisted birth remained significant at the age of 13 years (odds ratio=1.81), but not at 32 years, while no significant association with atopy was seen at either age.

Hancox and team conclude: "These findings support our hypothesis that a difficult childbirth requiring forceps assistance is associated with development of asthma and atopy, but that these associations may be, at least partly, explained by confounding factors."

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