Four fetal SNP alleles with the strongest univariate associations: paternally-transmitted IGF2 rs10770125 (P-value = 2 × 10–4) and INS rs2585 (P-value = 7 × 10–4), and maternally-transmitted KCNQ1(OT1) rs231841 (P-value = 1 × 10–3) and KCNQ1(OT1) rs7929804 (P-value = 4 × 10–3), were used to construct a composite fetal imprinted gene allele score which was associated with maternal glucose concentrations (P-value = 4.3 × 10–6, n = 981, r2 = 2.0%) and GDM prevalence (odds ratio per allele 1.44 (1.15, 1.80), P-value = 1 × 10–3, n = 89 cases and 899 controls). Here, KCNQ1 is linked to gestational diabetes.