The placental transfer of non-esterified fatty acids, predominantly in the direction of mother to fetus, is regulated on a gross scale by the transplacental non-esterified fatty acid gradient. This is maintained by fetal liver lipid uptake and by enhanced lipolysis of circulating triacylglycerol in the pregnant mother. It is also dependent upon maternal placental blood flow, which is reduced in diabetes, upon the fetal umbilical blood flow, upon maternal and fetal albumin concentrations and upon intratrophoblastic fatty acid binding protein, which appears to be altered in diabetes. Circulating maternal triacylglycerols also directly contribute non-esterified fatty acids to the fetus by intraplacental hydrolysis and the hypertriglyceridaemia associated with maternal diabetes, in concert with changes in lipase levels will enhance maternal to fetal lipid flux.