Maternal 25-hydroxyvitamin D concentration and offspring birth size : effect modification by infant VDR genotype

<b>Background/Objectives:</b> We tested the hypothesis that the relationship between maternal 25-hydroxyvitamin D (25-(OH)D) and offspring birth size differs according to offspring vitamin D receptor (VDR) genotype (Apa1, Bsm1, Fok1 or Taq1).<br /><br /><b>Subjects/Methods:</b> Mothers of 354 singleton babies had serum 25-(OH)D concentration measured at 28–30 weeks of gestation and consented to measurement of their babies soon after birth. DNA was extracted from the babies’ Guthrie cards.<br /><br /><b>Results:</b> There was evidence of effect modification by infant FokI genotype. Babies of deficient mothers had lower birth weight with FF or Ff, but not ff genotype (P-value for interaction after adjustment for potential confounding factors=0.02), but thicker subscapular and suprailiac skinfolds with ff, but not FF or Ff genotype (P=0.008 and 0.02, respectively). Sample size was insufficient to investigate effect modification by the other VDR polymorphisms.<br /><b><br />Conclusions: </b>These preliminary findings suggest that studies of maternal vitamin D status and birth size may need to take VDR genotype into account.<br />