“…Illumina arrays were the most widely used technique (N studies = 17 out of 23 studies), while a few studies used enzyme digestion-based tagging assay, 19,20 reduced representation bisulfite sequencing, 21 chromatin immunoprecipitation combined with DNA microarray, 22 targeted bisulfite sequencing, 23 and methylated DNA immunoprecipitation sequencing. 24 Peripheral blood was the most analyzed sample type (N = 15 studies), while a few studies used cord blood (N = 4 studies), 22,[25][26][27] saliva or buccal cells (N = 4 studies), 23,[28][29][30] neonatal blood spots samples (N = 1 study), 31 and placenta (N = 1 study). 32 The sample size of studied populations varied from 7 to 4133 children, which in most cases were European (N = 11) or from North America (N = 8), with low representation of other countries (N = 2 studies took place in Australia and 2 in China).…”