Our results of reduced expression of the type-II (Fast-Twitch)-associated genes, ACTN3 and MYBPC2, in L muscle are consistent with previous results from proteomics analyses in foetal IUGR muscle in pigs34, and with the finding that IUGR muscle contains reduced numbers of secondary fibres, from which most type II fibres derive22. Here, ACTN3 is linked to fetal growth restriction.