RPS6KB1 and fetal growth restriction: In humans, fetal growth restriction due to placental abnormalities of nutrient transport is associated with decreased S6K1 phosphorylation [90], but S6K1 phosphorylation is increased in the placenta of patients with gestational diabetes mellitus [91], which may be a compensatory response to promote fetal growth, as well as one of the mechanisms by which infants born with gestational diabetes mellitus become gigantic.