Maternal cigarette smoking during pregnancy is an independent predictor for symptoms of middle ear disease at five years' postdelivery.

Although an increasing body of literature has demonstrated a link between in utero exposure to cigarette smoke and childhood morbidity, the extent to which such exposure is associated with middle ear disease (MED) is less certain. We hypothesized that in utero exposure to cigarette smoke was associated with an increased risk of MED and aimed to calculate the proportion of disease at 5 years' postdelivery attributable to cigarette exposure during pregnancy. Methods. At their first antenatal session, 8556 women were enrolled in a prospective study of pregnancy. Mothers were followed during pregnancy, at birth, at 6 months' and at 5 years' postdelivery and completed a detailed questionnaire aimed at assessing the frequency of acute (<1 month) and subacute (1-3 months) symptoms of MED and ear surgery. The relationship between MED and smoking status during pregnancy was then examined and subsequently adjusted simultaneously for smoking status at other times and for other potentially confounding variables. Results. In the adjusted analyses, acute ear infections were associated with consumption of 1 to 9 cigarettes (OR: 1.6; 95% CI: 1.1-2.5), 10 to 19 cigarettes (OR: 2.6; 95% CI: 1. 6-4.2) and 20+ cigarettes (OR: 3.3; 95% CI: 1.9-5.9) per day at the first clinic visit. For subacute ear infections, an association was present with consumption of 10 to 19 cigarettes (OR: 2.6; 95% CI: 1. 4-5.0) and 20+ cigarettes (OR: 2.8; 95% CI: 1.3-6.0) at the first clinic visit. In utero exposure to 20+ cigarettes per day at the first clinic visit was also associated with an increased risk of ear surgery by 5 years' postdelivery (OR: 2.9; 95% CI: 1.3-6.6). These associations were independent of smoking at 6 months and at 5 years, age and gender of the child, breastfeeding history, maternal age, maternal education, maternal employment at 5 years, marital status at 5 years, socioeconomic status, use of day care, and the number of siblings or children in the household. A population attributable risk percent at 5 years of 39.4% for acute ear infections, 37.9% for subacute ear infections, and 30.0% for previous ear surgery was found for in utero exposure to cigarette smoke at the first clinic visit. Conclusions. Smoking at the first clinic visit was associated with an increased risk of MED and ear surgery at 5 years of age. The frequency of maternal smoking in the general population gives rise to a high population attributable risk percent for MED. Therefore, it is a significant contributor to childhood morbidity and provides another reason why women should be encouraged to avoid smoking during pregnancy.