The pregnancy-specific glycoproteins (PSGs) are the most abundant trophoblastic proteins in maternal blood during human pregnancy and they appear to be exclusive to species with hemochorial placentation. In human, the PSG gene family consists of 11 closely related genes that form a subgroup of the carcinoembryonic antigen (CEA) gene family on 19q13.2. High levels of PSG biosynthesis are restricted to the placenta syncytiotrophoblast and are essential for the maintenance of normal gestation in mammalian species. The regulation of T-cell function during pregnancy is likely the result of significant hormonal changes and may well involve immunoregulatory proteins derived from the placenta. Pregnancy-specific glycoproteins (PSGs) are the most abundant placentally derived glycoproteins in the maternal serum. The levels of PSGs are highest during the third trimester of pregnancy, a time marked by the most profound suppression of multiple sclerosis (MS) disease attacks.