Percent differences in methylation at the H19 and IGF2 DMRs in male and female infants in relation to maternal smoking status during pregnancy. For each DMR, the average difference in methylation is shown (+/− SEM) on the y-axis for male and female infants born to mothers who quit smoking during pregnancy (grey bars) or never smoked cigarettes (white bars) as compared to infants born to mothers who smoked throughout pregnancy (current smokers; baseline methylation). There was no significant difference at the H19 DMR for n=206 males (quit: −0.8% methylation difference, p=0.61; never: −2.4% methylation difference, p=0.13) or n=193 females (quit: +1.9% methylation difference, p=0.32; never: +1.1% methylation difference, p=0.54). The IGF2 DMR also showed no significant difference for n=151 females (quit: −0.6% methylation difference, p=0.73; never: −0.9% methylation difference, p=0.51) while male infants (n=169) born to current smokers showed significantly elevated methylation relative to those born to mothers who quit smoking during pregnancy (−6.5% difference, p<0.0001) and those born to mothers who never smoked (−4.7% methylation difference, p=0.0002).