GH1 and fetal growth restriction: Studies have shown that arginine supplementation can reduce the expression of placental apoptotic genes, improve placental function, stimulate the secretion of growth hormone in pregnant women, regulate NO and polyamine synthesis in the placenta, and increase the supply of oxygen and nutrients in the placental blood.16 In addition, arginine can also promote the synthesis of placental proteins and the development of fetal intestine through the mTOR signaling pathway, thereby improving IUGR.16 Arginine generally exerts its effects in early pregnancy.