In the form of 25(OH) cholecalciferol, vitamin D is transferred from the mother to the fetus in relatively small amounts that do not appear to cause maternal depletion. Those women who obtain adequate exposure to ultraviolet light do not need higher amounts during pregnancy. However, if usual intake declines below 150IU (3.8 mg)/day at high latitudes (where there is little ultraviolet radiation in the winter, such as in France), evidence of low maternal 25(OH) cholecalciferol and infant depletion has been observed at delivery.
The recommendation for both adolescent and adult women is to continue to consume the amount recommended as adequate (the Adequate Intake (AI)) for nonpregnant women, 5 mg (200IU/day). The UL of 50 mg (2000 IU/day) is the same as before pregnancy, based on prevention of high serum calcium concentrations. In the United Kingdom, the recommended intake is higher at 10 mg/day, which is probably appropriate based on its generally more northern latitude (thus less ultraviolet radiation) and lower synthesis of the vitamin in skin.
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