Sheep are normally managed within grazing systems; forage availability and quality are dependent upon seasonal conditions such as drought and humidity. It is therefore important for producers to know when during gestation it is critical to supplement animals with additional feed. Previous research has shown that nutrient restriction during mid-gestation causes a decrease in umbilical blood flow with a possible consequent decrease in fetal body weight and size. Our findings indicate that a decrease in umbilical blood flow upon nutrient restriction during mid-gestation is not solely a consequence of the restriction itself or an additional effect of parity. Moreover, it appears very probable that such a decrease is also an effect of maternal age during pregnancy. In order to address this question further investigation is needed.