A) Illustration depicting the plan of study. The F1 represents the maternal grandmother, F2 the mother in this study when she was a fetus, and F3 the child born when the mother matured. ( B) A-clustering followed by differential methylation analysis by generalized estimating equation (GEE) revealed 115 CpG clusters mapping to 346 CpG sites differentially methylated in child’s neonatal blood spots (CNBS) with high BLL in mother’s neonatal blood spot (MNBS) compared to CNBS with low BLL in MNBS. We observed more hyper-methylated CpG clusters (n = 98) compared to hypo-methylated CpG clusters (n = 17) at an exposure effect cut-off of 0.05 (5%) and an FDR p-value ≤ 0.05. ( C) Differential methylation analysis revealed no association between DNA methylation levels in a child’s current blood spot (CCBS) and mother’s neonatal BLL (n = 14). ( D) Overlap between the 320 CpG sites mapping to 116 clusters identified in a previous study , and the 564 CpG sites mapping to 183 clusters identified in this study. The 320 CpG sites (CCBS postnatal) correspond to the effects of BLL in CNBS on CCBS DNA methylation that we reported earlier 3 . The 564 CpG sites (CNBS prenatal) correspond to the effects of BLL in MNBS on CNBS DNA methylation that we report in this study ( 3 Fig. 1B). Note children recruited for the previous study are the same as in this study.