In order to elucidate the mechanism for pathogenesis of fetal macrosomia ("gigantism") in diabetic Pregnancy, metabolisms of DNA and Proteins in rat fetus and placenta will be studied. In diabetic pregnancy, the increase in the contents of nitrogen and DNA in the fetus is more readily detectable and occurs prior to the increase in the fetal weight itself. Therefore, the effects of maternal diabetes on the rates of accretions and the rates of syntheses of DNA and proteins will be measured at different stages of fetal development. In attempts to locate the biochemical site responsible for the changes in DNA synthesis, DNA polymerase activities in fetus and placenta will be measured.