The placental metabolism of vitamin A

Abstract The importance of the nutritional status of the fetus at the time of delivery is well recognized, and recent work has tended to indicate that fetal deficiencies—particularly of vitamin A—may be responsible for congenital abnormalities. 1, 2 Since the nutrition of the fetus depends not only on the maternal dietary intake, but, to an even greater extent, on the adequacy of transmission across the placental barrier, it becomes of increasing importance that the mechanism of such transmission be understood. The present paper reports an investigation of the placental metabolism of vitamin A. In general, previous studies of vitamin A in the nutrition of the human fetus have been confined to determinations of the maternal and fetal plasma levels of carotene and of the vitamin. 3 Williamson has called attention to the placenta, however, by suggesting that in the rat the transfer of vitamin A across that organ is inversely proportionate to the placental fat content. 4 Furthermore, in the course of the previous work on the fetal metabolism of vitamin C, 5, 6 a knowledge of the placental levels proved invaluable. Accordingly, the status of the fetal nutrition with vitamin A has been reviewed from the point of view of its placental metabolism.