Effect of vitamin A status at the end of term pregnancy on the saturation of retinol binding protein with retinol

Background: Vitamin A (retinol), which is required for normal fetal develop ment and successful gestation, circulates in the blood bound to a specific protein, the retinol binding protein (RBP). Little is known about the trans port and metabolism of this complex protein or about retinol status during normal human pregnancy. Objective: The aim of this study was to assess retinol status and transport modalities of retinol in well-nourished women with normal pregnancies, a p opulation poorly investigated compared with pathologic and malnourished pre gnant women. Design: The maternal blood and cord blood concentrations of retinol, vitami n E, beta-carotene, RBP, and transthyretin of pregnant French women at term (n = 27) were measured and compared with values from a nonpregnant control group (n = 27). In addition, holo-RBP (retinol bound), apo-RBP (retinol fr ee), and total protein were assessed in both groups to enable the hemodilut ion occurring during pregnancy to be taken into consideration and to evalua te the extent of saturation of REP with retinol. Results: Healthy pregnant women at term had normal serum circulatory amount s of retinol, vitamin E, binding proteins, and beta-carotene. However, they had less binding of retinol to REP (holo-RBP: 49.9% in pregnant women, 54. 0% in cord blood, and 77.5% in the control group). Conclusion: The results of this study suggest that retinol homeostasis and transport are modified during normal human pregnancy.