THE EFFECT OF MATERNAL UNDERNUTRITION ON THE GROWTH AND DEVELOPMENT OF THE GUINEA-PIG PLACENTA

Fetal growth is known to be correlated with the size of the placenta a nd the exchange surface area. Reduction in the growth of the materno-f etal exchange surface areas may be a mechanism by which the effects of maternal undernutrition on fetal growth are mediated. In the compact placenta of the guinea pig the exchange surface is equivalent to the p eripheral labyrinth. The effect of a 40% reduction in maternal feed in take on the growth of the peripheral labyrinth was investigated in pre gnant guinea pigs between gestational days 25 and 65. Fetal and placen tal weights were significantly reduced in the last trimester by 32% an d 38% respectively (P<0.01). Placental efficiency in early gestation w as significantly impaired in restricted animals but equivalent to ad l ib. fed controls by the last trimester. The volume of the peripheral l abyrinth increased as a percentage of the total placental volume with gestational age. Restricted placentae tended to be composed of a small er volume of peripheral labyrinth tissue in early gestation. It is sug gested that maternal undernutrition results in an impaired or delayed expansion of the peripheral labyrinth in early gestation causing a red uction in placental efficiency. By the last trimester the weight of th e peripheral labyrinth of restricted animals was reduced by 33% (P<0.0 5). The weight of the peripheral labyrinth was also significantly corr elated with fetal weight during the last trimester, suggesting that fe tal weight is limited by the size of the peripheral labyrinth in the l ater stages of gestation.