IGF-II associates with feto-placental growth in rodent and human. We determined three tag-single nucleotide polymorphisms (SNPs) to investigate haplotype frequency of IGF2 relative to size at birth in 134 healthy Japanese infants. In addition, a total of 276 healthy infants were investigated to determine whether common genetic variation of IGF2 might contribute to feto-placental growth using haplotype analysis. Further, quantitative methylation analysis of the IGF2/H19 was performed using the MassARRAY Compact system. In the initial study, the frequency of haplotype CTG from the paternal allele in small for date (SFD) infants was significantly higher than that in non-SFD infants (p = 0.03). In a second study, the CTG haplotype infants exhibited significantly lower birth length, weight, and placental weight compared with non-CTG infants. Further, the number of infants less than -1.5 SD (SD) birth weight in CTG haplotype was higher than those in non-CTG infants. There was no significant difference in the methylation status of H19/IGF2 in the two haplotypes. In conclusion, inheriting the IGF2 CTG haplotype from a paternal allele results in reduced feto-placental growth, but it is not associated with the methylation status of IGF2/H19.