Prenatal Tobacco Smoke Exposure Increases Hospitalizations for Bronchiolitis in Infants

Marcello Lanari; Silvia Vandini; Fulvio Adorni; Federica Prinelli; Simona Di Santo; Michela Silvestri; Massimo Musicco


Respiratory Research. 2015;16(152) 

In This Article


Of the 2,314 newborns, 104 were not available for the first scheduled follow-up interview and thus the remaining 2,210 (1,150 male and 1,060 female) were considered for this analysis. All of the infants survived the entire follow-up period. One hundred and 20 newborns (5.4 %) were hospitalized for bronchiolitis during the study period, most frequently during the very early period of life (54 % within the 3 month of life). In only 31 newborns hospitalized for bronchiolitis a laboratory test was carried-out resulting positive for RSV in 26 (83 %) cases. Parental socio-demographic and infants' characteristics are reported in Table 1 by hospitalization for bronchiolitis. Low level of parents' education, low gestational age and all the considered prenatal, neonatal and postnatal risk conditions were more frequent in infants hospitalized for bronchiolitis. Moreover, any exposure (pre and post-natal) to tobacco smoke was more frequently registered in children who were hospitalized for bronchiolitis

The different exposures and characteristics of the infants according to exposure to tobacco smoke during the prenatal and postnatal life are reported in Table 2. TSE (both prenatal and postnatal) was more frequent in babies born to parents with only primary education. Mothers smoking more than 15 cigarettes per day during pregnancy more frequently had newborns with low gestational ages. Maternal smoking of more than 15 cigarettes per day during pregnancy was associated with an increase of non-breastfeeding of the newborn. Presence of siblings was associated with TSE both of the mother during pregnancy and of the newborn in postnatal life period. Also, living in crowded living conditions was more frequent for newborns exposed to smoke in prenatal and postnatal periods.

Table 3 and Fig. 1 describe the association of tobacco smoke exposure and all considered risk factors, with the risk of hospitalization for bronchiolitis during the first year of life. At univariate analysis, the exposure to any tobacco smoke was associated with a 40 % increased risk of hospitalization (HR = 1.4, 95 % CI 1.0–2.1). When accounting for all the other considered variables in multivariable analysis, the risk was still increased however lost statistical significance (HR 1.3, 95 % CI 0.9–1.9). Moreover, when considering exposure to prenatal tobacco smoke, having a mother smoking more than 15 cigarettes every day or a mother exposed to second hand smoke were associated with a significant risk increase of 3.5 (CI 1.5–8.1) and of 1.7 (1.1–2. 6), respectively. In multivariable analysis these risks remained substantially equal in size and direction. As far as tobacco exposure in postnatal period is concerned, only small non-significant risk increases were observed in univariate analysis that were no longer present in multivariable analysis. Among the other considered variables, the most remarkable results from the multivariable analysis were a negative association with mother's age and with increasing gestational age at birth, positive significant associations with all the environmental risk conditions and finally, no significant association with parent's educational level and with prenatal or perinatal risk conditions.

Figure 1.

Crude and Adjusted Hazard Ratios (HRs) for Prenatal and Postnatal Tobacco Smoke Exposure for bronchiolitis Hospitalization in the First Year of Life. Adjusted for mother's age (y), parents' educational level, wGA, prenatal risk conditions, neonatal risk conditions, exposure to epidemic season, breastfeeding, siblings, crowded living, day care attendance