Hemodilution and iron metabolism in rats during pregnancy.

Studies were made on the cellular components of the blood, the serum iron concentration, and the circulating blood and plasma volumes of rats in pregnancy and on the iron transport from the maternal blood to the conception products (uterus and its contents) using radioactive iron. Anemia of pregnancy developed and was most pronounced during late pregnancy when the conception products developed rapidly. The reticulocyte count did not increase significantly, so that there is no evidence for stimulation of hematopoiesis during pregnancy of rats. The circulating blood and plasma volumes increased significantly during late pregnancy, but the total hemoglobin and red cell volume did not increase. The anemia in pregnancy of rats was due to hemodilution, but this hemodilution occurred in different grades in comparison with human pregnancy. The iron concentration of the serum decreased most during late pregnancy when development of the conception products was greatest and placental transport of iron to the fetus was largest.