Eating for two? The unresolved question of optimal diet in pregnancy

Unequivocal evidence of the importance of fetal nutrition as a driver of intrauterine growth has come from a range of experimental studies in which nutrient supply to the fetus is manipulated (1). The dependence of the fetus on a sufficient supply of nutrients to support its successful growth and development highlights the importance of adequate maternal nutrition to ensure that fetal nutrient needs can be met. However, the complex supply chain between maternal diet and fetal nutrient supply means that fetal nutrition and maternal nutrition are not the same (1); and for human pregnancies, the definition of what is optimal, in terms of maternal diet before and during pregnancy, remains unknown. Across the world, diets vary hugely, both in quantity and quality, and even in developed settings there is significant variation in the quality of young women’s diets, with consequent differences in patterns of micro- and macronutrient intake (2). But do such variations in maternal diet matter to the fetus?