Relationship of fetal to placental size: the pig model

Placental weight and macroscopic surface area are closely correlated with fetal weight throughout the second half of gestation in the pig. The limiting effect of placental size on fetal weight becomes more obvious as gestation advances. Fetal weight/placental weight ratio increases as placental weight decreases. Within individual litters, lightweight placentas have up to 150% more macroscopic surface area per unit placental weight.