INS and fetal growth restriction: Therefore, the current study was designed to examine the independent effect of a prolonged, low dose insulin infusion directly into IUGR fetal sheep in vivo at 75% gestation (112 ± 1 to 126 ± 2 dGA), when myoblasts are in the process of rapid proliferation to form new myotubes and to fuse onto existing myofibers (22, 28).