these two values in the mothers, newborns of mothers who received the vitamin D supplement had a statistically higher serum calcium level on the fourth day of life than those from mothers with the lower vitamin D intake. Several studies have evaluated supplementation after the pregnant woman's first trimester with either 10 or 25 µg (400 or 1,000 IU)/day of vitamin D. It was concluded that vitamin D supplementation increased circulating concentrations of 25(OH)D in the mother (Anderson et al., 1988; Cockburn et al., 1980; Delvin et al., 1986; Mallet et al., 1986; Markested et al., 1986; Reddy et al., 1983) and may improve neonatal handling of calcium (Cockburn et al., 1980; Delvin et al., 1986).

During pregnancy, there is a gradual rise in a woman's serum 1,25(OH)2D concentration that is paralleled by an increase in her blood concentration of vitamin D binding protein (Bikle et al., 1984; Bouillon et al., 1981). However, during the last trimester, the woman's serum 1,25(OH) 2D level continues to rise without any change in the vitamin D binding protein level, causing an increase in the free concentration of 1,25(OH) 2D. Evidence is strong that the placenta metabolizes 25(OH)D to 1,25(OH) 2D and therefore contributes to the maternal and possibly fetal blood levels of 1,25(OH)2D (Gray et al., 1979; Weisman et al., 1979).

AI Summary: Pregnancy

Although there is ample evidence for placental transfer of 25(OH)D from the mother to the fetus (Paunier et al., 1978), the quantities are relatively small and do not appear to affect the overall vitamin D status of pregnant women. Women, whether pregnant or not, who receive regular exposure to sunlight do not need vitamin D supplementation. However, at vitamin D intakes less than 3.8 µg (150 IU)/day, pregnant women during the winter months at high latitudes had a mean 25(OH)D concentration of 9.1 ng/ml (22.75 nmol/liter) at delivery (Paunier et al., 1978). Thus, there is no additional need to increase the vitamin D age-related AI during pregnancy above that required for nonpregnant women. However, an intake of 10 µg (400 IU)/day, which is supplied by prenatal vitamin supplements, would not be excessive.

AI for Pregnancy

14 through 18 years

5.0 µg (200 IU)/day

 

19 through 30 years

5.0 µg (200 IU)/day

 

31 through 50 years

5.0 µg (200 IU)/day



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