Type 1 diabetic women have a decrease in insulin requirements during early pregnancy. Preliminary evidence suggests this decrease may be secondary to the regeneration of pancreatic B-cells during pregnancy During the second and third trimesters, insulin requirements in Type 1 diabetic women progressively increase until approximately 36 weeks gestation at which time there is a plateau, and frequently, a drop in insulin requirements. We hypothesize that there is regeneration of pancreatic islet cell mass in Type 1 diabetic women during pregnancy. In a cross-sectional study, we will use the acute insulin c-peptide response to arginine to determine if pancreatic islet mass increases at 12 and 36 weeks gestation. Type 1 diabetic women who are not pregnant, who are at 12 and 36 weeks gestation, and who are 6 weeks post-partum will undergo an intravenous arginine tolerance test following an overnight fast. If we find that there is regeneration of beta cells it opens the possibility that therapy may be directed to the same end for people with Type 1 diabetes.