Table 1.

Pathways linking maternal exposures to fetal exposures

	Pathway A	Pathway B
	Essential nutrient	Macronutrient
Examples	Vitamins (A, C, D, E, K and B complex), minerals (i.e. iron, copper, zinc, fluoride, selenium)	Carbohydrates (i.e. glucose), protein (amino acids), fatty acids
Effect on development	Co-factors in metabolic processes; deficit leads to developmental impairment	Energy substrate and building blocks of all cells and tissues; primary drivers of growth and metabolic programming
Quantity	Trace quantities are typically required for healthy development	Large quantities are required
Source	Diet, maternal stores	Diet, maternal stores and other metabolic precursors
Buffering capacity	Buffering of dietary deficits by maternal stores	Circulating levels are homeostatically maintained with input from diet, extensive bodily stores and metabolic interconversion between substrate types
Effect of nutritional intervention in pregnancy on fetus	If maternal stores depleted, can have direct/immediate effects	Dietary nutrients enter maternal metabolism which dampens direct effects on current pregnancy
Recommended intervention targets	Supplementing maternal intake during and prior to pregnancy	Supplementing during mother's own early development and across life course