Beyond birthweight: the maternal and placental origins of chronic disease.

New findings on the maternal and placental programming of chronic disease lead to four conclusions: (1) Growth of the placental surface is polarized from the time of implantation, so that growth along the major axis, the length, is qualitatively different from growth along the minor axis, the breadth. (2) The human fetus may attempt to compensate for undernutrition by expansion of the placental surface along its minor axis. This only occurs if the mother was well nourished before conception, and may have long-term costs that include hypertension. (3) The effects of placental size on long-term health are conditioned by the mother's nutritional state, as indicated by her socio-economic status, height and body mass index. (4) The maternal-placental programming of chronic disease differs in boys and girls. Boys invest less than girls in placental growth but more readily expand the placental surface if they become undernourished in mid-late gestation. Boys are more responsive to their mothers' current diets while girls respond more to their mothers' lifetime nutrition and metabolism.