Michael C Kew1,2 1Department of Medicine, Groote Schuur Hospital, University of Cape Town, Cape Town, 2University of the Witwatersrand, Johannesburg, South Africaα-FP is an α1-globulin present in high concentration in the fetal serum of mammals. It is the dominant plasma protein in the developing embryo, and is synthesized by the embryonal liver, by the endodermal cells of the visceral yolk sac, and, in very small amounts, by the embryonal intestine.1 Approximately 80% of fetal hepatocytes synthesize and secrete α-FP. The protein has been closely conserved throughout phylogenesis, suggesting that it has functions essential to the fetus, although precisely what these functions are remains to be learned. There does, however, appear to be an inverse relationship between serum α-FP and albumin levels, suggesting that α-FP might function as fetal albumin.2 Other possible biological properties of the α1-globulin include binding to estrogens and bilirubin, immunosuppressive activity, and a growth-promoting potential.3 The serum level of the protein remains constant until week 32, when it begins to sharply decrease. After birth, production of α-FP normally remains completely repressed, and serum concentrations are correspondingly very low.