Aims:

We (Joubert et al. Environ Health Perspect. 2012;120:1425-31) and subsequently others have identified replicable methylation differences at birth in relation to maternal smoking using the Illumina 450K platform. Some of the same changes have been seen in adult smokers. It is not known whether these differences persist to later childhood, whether the persistence may differ across loci, or whether postnatal exposure might contribute to the persistence of these methylation changes. We propose to analyze ALSPAC data in the setting of meta-analysis across cohorts with data on maternal smoking during pregnancy and offspring Illumina 450K methylation and asthma phenotypes to address the following specific aims:

1. Do methylation differences at specific loci related to maternal smoking detected at birth persist to later childhood, taking into account postnatal exposure to smoking.

2. To examine the association between maternal smoking during pregnancy, assessed by plasma cotinine, and the development of asthma phenotypes in the child.

3. Investigate whether methylation differences at birth related to maternal smoking may be a biomarker of the risk of developing asthma phenotypes from exposure to maternal smoking during pregnancy.