MedWire News: Exclusive breastfeeding for at least 6 months can protect infants against early respiratory allergy, but maternal smoking negates this benefit and may even increase the risk, claim investigators.

They stress, however, that the findings should encourage new mothers who smoke to give up smoking rather than avoid breastfeeding.

Hemila Guedes (University Hospital, Salvador, Brazil) and co-workers prospectively studied 268 children from birth until 5 years of age.

Exclusive breastfeeding for at least 6 months significantly reduced the risk for developing respiratory allergies over the first 5 years of life, at an odds ratio of 0.33. Children breastfed for fewer than 6 months were 2.34 times more likely than children breastfed for longer to develop respiratory allergies.

However, in children whose mothers smoked, the benefits of breastfeeding in the first year were lost. Moreover, the risk for respiratory allergies in children born to mothers who smoked increased with the duration of breastfeeding.

Indeed, the researchers report that children born to mothers who smoked and breastfed for more than 6 months were nearly five times as likely to develop respiratory allergies as their peers born to non-smoking mothers, while children born to mothers who smoked and breastfed for only up to 6 months were twice as likely to develop respiratory allergies.

Discussing the reasons behind their findings in the journal Pediatric Allergy and Immunology, Guedes et al speculate that “the closer contact of the baby with smoke or even cigarette smell during breastfeeding may enable an intense and more frequent irritation of the respiratory tracts.”

Alternatively, “allergenic substances may be transferred through breast milk, increasing the risk for allergic manifestations in first childhood,” the researchers say.

Whatever the underlying mechanisms, the investigators conclude that “the information obtained supports the need for educational initiatives encouraging the practice of breastfeeding and warning of the risk of smoking, to reduce not only the frequency of allergic symptoms but also other morbid conditions.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a part of Springer Science+Business Media. © Current Medicine Group Ltd; 2009

Free abstract