The growth hormone (GH)-insulin-like growth factor axis plays a critical role in fetal and placental development and the maternal adaptation to pregnancy. Despite this, its regulation in pregnancy is not well understood. In humans, placental secretion of GH suppresses pituitary GH secretion and replaces the pulsatile pattern of early pregnancy with stable moderate-high concentrations in the second half of pregnancy. Placentae of most mammals do not express GH, but do express hormones that regulate GH, including ghrelin and GHRH. How GH changes during pregnancy has been characterised in only a few species – in rat and pig circulating GH remains pulsatile throughout pregnancy, and we have recently demonstrated changes in patterns of pulsatile GH profiles during murine pregnancy. Fetal growth and placental function can be promoted by maternal administration of GH in non-human species, whilst responses appear to depend on the pattern of administration as well as nutritional status. This suggests that in pregnancy as in non-pregnant animals, GH action depends on patterns of exposure as well as concentrations. Maternal GH probably acts at least in part via stimulation of IGF1, which also promotes placental development and subsequent function. Manipulating the maternal GH-IGF1 pathway, particularly in early pregnancy during placental development, may therefore be an effective approach to improve fetal growth and pregnancy outcomes.