Maternal food restriction reduces the exchange surface area and increases the barrier thickness of the placenta in the guinea-pig

The extent to which maternal nutrition influences fetal growth through effe cts on placental functional development is unclear. Poor maternal nutrition is a major cause of poor fetal growth which increases neonatal morbidity a nd mortality, and may also increase the risk of several adult-onset disease s. We have therefore characterized the ontogeny of structural determinants df function in the placenta in guinea-pigs fed ad libitum or food restricte d from before and during pregnancy. Guinea-pigs were killed at days 30 and 60 (term 67 days) of pregnancy. In ad libitum fed animals, the surface dens ity (surface area/g placental labyrinth), which is a measure of the convolu tion of the exchange surface, doubled, while total surface area increased 1 8-fold between mid and late gestation. Concomitantly, the arithmetic mean b arrier thickness to diffusion across trophoblast decreased by 68 per cent. Late in gestation, food restriction reduced the proportion of the placenta devoted to exchange (labyrinth) by 70 per cent (P<0.04) and the weight of t he placental labyrinth by 45 per cent (P=0.001). Maternal food restriction also reduced the total placental surface area for exchange by 36 per cent a t day 30 (P=0.02) and 60 per cent at day 60 (P<0.0005) of gestation, and th e surface density of trophoblast by 36 per cent at day 30 (P=0.01) and 29 p er cent at day 60 (P=0.005) of gestation. The arithmetic mean barrier thick ness for diffusion was increased by maternal food restriction at both gesta tional ages (day 30, +37 per cent, P=0.008, and day 60, +40 per cent, P=0.0 1). These findings suggest that maternal food restriction not only reduces fetal and placental weights, but also induces structural alterations in the placenta that indicate functional impairment beyond what would be expected for the reduction in its weight. (C) 2001 Harcourt Publishers Ltd.