Few studies provide information about the selenium requirements of pregnant women. However, the pregnancy requirement should allow accumulation of enough selenium by the fetus to saturate its selenoproteins. Based on an estimated selenium content of 250 µg (3.2 µmol)/kg body weight (Schroeder et al., 1970), a 4-kg fetus would contain 1,000 µg (12.6 µmol) of selenium. This need could be met by an additional 4 µg (0.05 µmol)/day of selenium over the 270 days of the pregnancy. Based on this, an additional requirement of 4 µg (0.05 µmol)/day during pregnancy is estimated.

Reported selenium intakes of uncomplicated pregnancies have varied considerably. Levander et al. (1987) found that the average selenium intake of apparently healthy pregnant females in the United States was 73 µg (0.92 µmol)/day. Swanson et al. (1983) have shown that mean selenium retention in women fed a high-selenium diet (150 µg [1.9 µmol]/day) was 21 µg (0.27 µmol)/day in early pregnancy and 34 µg (0.43 µmol)/day in late pregnancy compared to 11 µg (0.14 µmol)/day for nonpregnant females. However, mean selenium intakes as low as 28 µg (0.35 µmol)/day have been reported for pregnant women in New Zealand without obvious ill effects for the newborn (Thomson and Robinson, 1980).

Based on a fetal deposition of 4 µg (0.05 µmol)/day throughout pregnancy, the EAR is increased by 4 µg (0.05 µmol)/day during pregnancy. Since most selenium is highly bioavailable, no adjustment is made for absorption. No adjustment is made for the age of the mother.

The RDA for selenium is set by assuming a coefficient of variation (CV) of 10 percent (see Chapter 1) because information is not avail-