The influence of maternal nutrient restriction in early to mid-pregnancy on placental and fetal development in sheep

Placental weight is a primary factor determining size at birth in many spec ies. In sheep, placental weight peaks at approximately mid-gestation, with structural remodelling occurring over the second half of pregnancy to meet the increasing nutritional demands of the growing fetus. Numerous factors i nfluence placental growth and development in sheep, and many workers (see K elly, 1992) have investigated the role of maternal nutrition as a regulator of placental and fetal size. We have studied the effects of feeding ewes a pproximately 50% of their recommended energy requirements during early to m id-pregnancy on fetal and placental indices measured at mid-gestation (i.e. 80 d) and close to term (i.e. 145 d). Maternal nutrient restriction is ass ociated with a reduction in placental weight at 80 d, but an increase in pl acental weight at 145 d of gestation, compared with ewes fed adequately in early pregnancy. No significant effect on fetal weight was observed at eith er 80 or 145 d gestation, although differences in body dimensions and the i nsulin-like growth factor-1 axis were found in lambs from nutrient-restrict ed ewes delivered close to term. Maternal nutrition during pregnancy plays a pivotal role in the regulation of fetal and placental development in shee p, and therefore has the potential to influence both short- and longer-term health outcomes.