1. As part of a more general descriptive study Bergmann et al10 related cord blood IgE levels to parental smoking habits during pregnancy for 4793 German infants, representing 63% of all babies born in six hospitals during 1990. The prevalence of elevated IgE concentrations ([0.7 kU/l) was 11.6% among 3495 offspring of non-smoking mothers and 10.6% among 1298 babies whose mothers smoked during pregnancy (odds ratio 0.9, 95% CI 0.7 to 1.1). The equivalent odds ratio for paternal smoking was 1.0 (95% CI 0.8 to 1.2). This large study did not report upon possible effect modification by atopic family history
2. Two earlier studies5 12 of small samples (46 and 136 infants, respectively) also report no significant association of parental smoking with neonatal IgE concentrations, but another of 215 infants found a positive correlation between the number of cigarettes smoked in pregnancy and cord blood IgE levels.13 A somewhat larger study of 325 infants found no significant association using a more sensitive assay, but it appears to have been published only in abstract form.14 These studies offer insufficient quantitative information to be considered in detail in this review
3. Ronchetti et al21 measured total serum IgE concentrations in 159 nine year old children, 89% of a randomly selected sample in three Italian towns. An association of geometric mean IgE with one or more parents smoking emerged for boys (99 versus 39 kU/l) but not for girls (56 versus 59 kU/l). Statistical significance was achieved by subgroup analysis, but the interaction of sex and parental smoking was not formally assessed. The prevalence of eosinophilia ([4% leucocytes) was also increased in the offspring of smoking parents, independent of the common association with IgE level. This otherwise informative study does not provide an estimate of the effect of parental smoking on serum IgE levels in both sexes combined, although it is reported to be nonsignificant (p=0.2)
4. The relationship of current maternal smoking to atopy, defined as [5 mm erythema or a detectable weal ([0 mm) to any of four aeroallergens, was analysed among a population based cohort of 196 children aged 12–16 in Boston, Massachusetts.24 A positive association of similar strength to the Italian study was found (odds ratio 2.2, 95% CI 1.1 to 4.4). This was significant at the 2% level and the 95% confidence interval is derived from the published 2 value
5. A longitudinal study of consecutive births in the Isle of Wight during 1989–90 has reported on the association of environmental factors and allergic sensitisation at the ages of one26 and two years.27 Only the latter study is considered here. Among the offspring of 257 smoking mothers 4.7% had positive skin prick tests to one or more of five allergens at the age of two compared with 5.3% of 915 children of nonsmoking mothers, an odds ratio of 0.9 (95% CI 0.5 to 1.7). It is not clear from the publication whether this relates to current maternal smoking or smoking in pregnancy