Pregnancy is associated with a marked increase in the number of pancreatic beta cells in response to the increased insulin demand. In rats and mice the growth of the beta cell mass is primarily due to proliferation of the existing beta cells resulting in enlargement of the islets of Langerhans. However, in a study of islets in human pregnancy (Butler et al 2010) the beta cell mass was found to be increased by numerous small islets and no sign of proliferation, suggesting that the growth of the beta call mass is due to neogenesis from putative progenitor/stem cells. In the proposed project we want to test the hypothesis that neogenesis rather than proliferation of beta cells is involved for the expansion of the beta cell mass in human pregnancy. This will be performed by immunochemical staining for prolactin receptors, Ngn-3 and Pdx-1 as markers of beta cell regeneration in pancreatic sections from pregnant women.