Maternal nutrition in late gestation and placental growth

In sheep, placental mass peaks by midgestation, after which the placenta undergoes an appreciable amount of structural remodeling that enables the increased fetal nutrient requirements during late gestation to be met. For adequately fed females, this may be accompanied by a significant decline in placental mass. Maternal undernutrition of ewes during early to mid-gestation (30-80 days; term = 147-150 days) followed by adequate nutrient intake for the remainder of the gestation is associated with a failure to observe the expected decline in placental weight at term. Similarly, maternal undernutrition from 115 days' gestation to term results in a heavier placenta. Neither of these nutritional manipulations reduces the weight or dimensions of the newborn, but they can reduce viability after birth. These alterations in placental to fetal weight ratios could be of longer-term importance as they have been implicated in the causes of hypertension in later life. An increased understanding of the nutritional and endocrine factors contributing to enhanced placental mass in late gestation is likely to be beneficial in improving newborn health and survival.