Prenatal tobacco exposure is associated with asthma dependent on 17q12-21 genotype, exacerbations, increased lower respiratory tract infections, impaired lung function, and increased bronchial responsiveness in children aged 0 to 7 years, although it is not associated with allergies, according to the results of a recent study published in the European Respiratory Journal.
Investigators in Denmark analyzed data from the Copenhagen Prospective Studies on Asthma in Childhood 2000 (COPSAC2000) birth cohort with clinical follow-up on cohort children until 7 years of age. Outcomes related to asthma, exacerbations, lung function, lower respiratory infections, and allergy were compared in children who were exposed to prenatal tobacco vs those who were not. Prenatal tobacco exposure was determined by maternal smoking during the third trimester.
Among the 411 children in the birth cohort, 63 were exposed to tobacco smoking prenatally and 348 were not exposed. Investigators found that children exposed during pregnancy had a doubled risk of developing asthma, a tripled risk of exacerbations, a doubled risk of lower respiratory tract infections, reduced lung function, and increased bronchial responsiveness by age 7 compared with children who were not exposed, though there was no association between tobacco exposure and allergy risk. Notably, the effect of prenatal tobacco exposure on asthma (though not on other outcomes) depended on 17q12-21 genotype, with an increased risk only among children without risk alleles.
Children exposed to tobacco prenatally also had lower birth length and weight, had lower social circumstances, and were more often exposed to passive smoke during childhood.
The study authors wrote, “These findings suggest that prenatal tobacco exposure predominantly has adverse lung developmental/structural effects in utero, leading to diminished lung function and increased risk of non-atopic asthma.”
Sunde RB, Thorsen J, Pedersen CT, et al. Prenatal tobacco exposure and risk of asthma and allergy outcomes in childhood. Eur Respir J. Published online July 8, 2021. doi:10.1183/13993003.00453-2021