Chunk #19 — MATERIALS AND METHODS — Statistical methods — Analysis of the association between rs1051730 genotype and the odds of continued smoking in pregnancy.
We selected women reporting smoking regularly immediately before becoming pregnant (ALSPAC: n = 2241; EFSOCH: n = 233). We pooled subjects from both studies for analysis, after verifying that there was no difference in allele frequency (P = 0.35). Patients were classified, using data collected on first trimester smoking, as ‘stopped smoking’ or ‘continued to smoke’. A similar dichotomous variable was created using data on third trimester smoking (assessed in ALSPAC at 32 weeks and EFSOCH at 28 weeks gestation). We performed logistic regression (multiplicative model) to assess the association between each dichotomized variable and number of copies of the rs1051730 risk allele carried, adjusting for study. In the separate studies, we repeated the logistic regression analysis including known covariates of smoking cessation in pregnancy.
