Epidemiological studies have shown that infants exposed to an increased supply of nutrients before birth are at increased risk of type 2 diabetes in later life. We have investigated the hypothesis that fetal overnutrition results in reduced expression and phosphorylation of the cellular fuel sensor, AMP-activated kinase (AMPK) in liver and skeletal muscle before and after birth. From 115 d gestation, ewes were fed either at or ~55% above maintenance energy requirements. Postmortem was performed on fetuses at 139-141 d gestation (n=14) and lambs at 30d of postnatal age (n=21) and liver and quadriceps muscle collected at each time point. The expression of AMPK1 and AMPK2 mRNA was determined by qRT-PCR. The abundance of AMPK and Phospho-AMPK (P-AMPK) was determined by Western Blot and the proportion of the total AMPK pool that was phosphorylated in each sample (%P-AMPK) determined. The ratio of AMPK2 to AMPK1 mRNA expression was lower in fetuses compared to lambs in both liver and muscle, independent of maternal nutrition. independent of maternal nutrition. Hepatic %P-AMPK was lower in both fetuses and lambs in the Over Fed group and %P-AMPK in the lamb liver was inversely related to plasma glucose concentrations in the first 24 h after birth (r=0.73 ,P<0.025). There was no effect of maternal overnutrition on Total AMPK or P-AMPK abundance in liver or skeletal muscle. We have therefore demonstrated that AMPK responds to signals of increased nutrient availability in the fetal liver. Suppression of hepatic AMPK phosphorylation may contribute to increased glucose production, and basal hyperglycemia, present in lambs of Over Fed ewes in early postnatal life.