The influence of maternal pregnancy glucose concentrations on associations between a fetal imprinted gene allele score and offspring size at birth.

The fetal imprinted gene allele score was positively associated with birth weight (β = 63 (17-109) g/risk allele, β' = 0.113, p = 7.6 × 10-3, n = 405). This association was partially attenuated by adjusting for maternal glucose concentrations (β = 50 (4-95) g/risk allele, β' = 0.089, p = 0.03, n = 405). The allele score was also positively associated with risk of being large for gestational age at birth (odds ratio 1.60 (1.19-2.15) per risk allele, p = 2.1 × 10-3, n = 660) and negatively associated with risk of being small for gestational age at birth (odds ratio 0.65 (0.44-0.96) per risk allele, p = 0.03, n = 660). The large for gestational age at birth association was also partially attenuated by maternal glucose concentrations. These results suggest that associations between the fetal imprinted gene allele score and size at birth are mediated through both glucose-dependent and glucose-independent mechanisms.