Nutritional effects on foetal growth

The emphasis in nutritional studies on foetal growth has now moved from the last trimester of pregnancy, when most of the increase in foetal size take s place, to earlier stages of pregnancy that coincide with foetal organogen esis and tissue hyperplasia. At these stages absolute nutrient requirements for foetal growth are small but foetal metabolic activity and specific gro wth rate are high. It is thus a time when nutrient supply interacts with ma ternal factors such as size, body condition and degree of maturity to influ ence placental growth and set the subsequent pattern of nutrient partitioni ng between the gravid uterus and maternal body. Throughout pregnancy the maternal diet controls foetal growth both directly , by supplying essential nutrients and indirectly, by altering the expressi on of the maternal and foetal endocrine mechanisms that regulate the uptake and utilization of these nutrients by the conceptus. Nutritional effects o n the endocrine environment of the embryo during the early stages of cell d ivision can alter the subsequent foetal growth trajectory and size at birth ; so too can current in vitro systems for oocyte maturation and embryo cult ure up to the blastocyst stage. There is increasing evidence that subtle al terations in nutrient supply during critical periods of embryonic and foeta l life can impart a legacy of growth and developmental changes that affect neonatal survival and adult performance. Identifying the specific nutrients that programme these effects and understanding their mode of action should provide new management strategies for ensuring that nutritional regimens f rom oocyte to newborn are such that they maximize neonatal viability and en able animals to express their true genetic potential for production.