Abstract
Summary
Pregnant rats were rendered severely anemic by permitting free bleeding from the freshly severed tail on 3 successive days. This frequently caused early termination of pregnancy as a result of maternal death or resorption of the entire litter, but litters from mothers surviving this treatment were essentially normal. Only when bleeding was begun on the 9th day was there a minimal effect on the offspring, manifested by malformations in 2.6% of the young, a mild degree of retardation of growth in 4 of 13 litters, and a slight increase above the normal rate of intrauterine resorption in litters reaching term. Since even these minimal effects were not observed after hemorrhage at other times during gestation, it is apparent that maternal hemorrhagic anemia represents no particular hazard to the offspring in surviving litters. This suggests that severe physiologic stresses during pregnancy, however severe, are not always capable of causing abnormality in the offspring.
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