Moderately preterm births add to asthma burden

Nov 13 2013

Research from Finland shows that children born late preterm or early term are at significantly increased risk for asthma compared with those born at term, and these births account for the majority of excess asthma burden due to prematurity.

The study also indicates that late- and post-term births may actually have a protective effect against asthma development.

The team, led by Maijakaisa Harju (Kuopio University Hospital), analyzed data from 44,173 women who gave birth at their institution between 1989 and 2008 and whose offspring could be linked to the national social insurance database up to the age of 19 years.

Overall, 6% of these children had asthma during childhood, as evidenced by claims for anti-asthma medication. The team notes that this corresponds to a previously reported estimate of asthma prevalence in Finland.

The researchers found that those children born very and moderately prematurely, at 32 weeks’ gestation or earlier, had the highest prevalence of asthma, at 17.8%. This equated to a 3.9-fold increased odds for the condition, after adjustment for maternal and neonatal factors, compared with children born at term (39–40 weeks), for whom the prevalence was 5.5%.

And, while the odds for asthma went down with decreasing prematurity, children born late preterm (33–36 weeks) or early term (37–38 weeks) still had significantly increased odds compared with children born at term, at 1.7-fold and 1.2-fold, respectively. Of an estimated 364 extra cases of asthma associated with prematurity in their sample, the authors calculate that 54.7% of these were related to late preterm or early term births.

By contrast, children born at 41 weeks or later had a lower prevalence of asthma, at 5.0%, equivalent to a 10% reduction in odds versus children born at term.

The authors also note that male gender and maternal asthma seemed to have a more significant impact on asthma risk in children born at term while being of minor significance in those born preterm.

“[T]o decrease the risk of asthma, it is advisable to avoid iatrogenic early term or late preterm delivery and to continue pregnancy as far as possible,” the authors write in the Journal of Pediatrics, adding that “this may be particularly important in pregnant women with asthma.”

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