Fig. 4

The effect of maternal smoking on methylation change. a The effect of maternal smoking on methylation change of cg09836827 (VWF) in the age 0–4/5 group. Maternal smoking shows an enhanced effect on decreasing methylation levels since the decrease from age 0 to age 4/5 years old of cg09836827 in the exposed group is significantly larger compared to the non-exposed group. b Density plot of effect size of all nominally significant a-DMSs (P < 0.05) with maternal smoking. In the age 0–4/5 group, methylation changes tend to be negatively associated with maternal smoking since there are more negatively associated a-DMSs. In the age 4–8 group, there are similar numbers of negatively- and positively associated sites