How much selenium do you need during pregnancy?

What does the evidence say about selenium during pregnancy?

1. The selenium RDA is 60 mcg a day in pregnancy and 70 mcg a day during lactation, against 55 mcg for non-pregnant adults, with a tolerable upper intake level of 400 mcg a day that applies in pregnancy and lactation too. 1
2. Food can carry you past the RDA in a single serving: Brazil nuts contain 544 mcg of selenium per ounce, roughly 68 to 91 mcg per nut, while 3 ounces of tuna provides 92 mcg, sardines 45 mcg and shrimp 42 mcg. 1
3. Selenium does not act alone. A New Zealand study of pregnant and breastfeeding women noted that low maternal serum selenium concentrations are associated with adverse pregnancy outcomes such as pre-eclampsia, other types of pregnancy-induced hypertension and preterm birth, and that selenium deficiency could potentially worsen the consequences of mild iodine deficiency. 2
4. Low selenium status has been linked to adverse pregnancy outcomes in observational work: selenium concentrations are significantly lower in women with pre-eclampsia than in normal pregnancy, lower first-trimester levels raised fetal growth restriction risk by 11 percent, and women in the lowest selenium quartile at or below 56.60 mcg/L had about three times the risk of a small-for-gestational-age baby. 3
5. In the Norwegian Mother, Father and Child Cohort Study, low maternal selenium intake below 30 mcg a day was associated with increased risk of neonatal morbidity and intervention, while intakes above 120 mcg a day showed no direct association with adverse neonatal outcomes. 4

Is selenium safe in each trimester?

• First trimester. Placental selenoproteins are part of the early antioxidant picture, which is why low status draws attention here. In one analysis, women with circulating selenium in the lowest quartile, at or below 56.60 mcg/L, had roughly three times the risk of a small-for-gestational-age baby.
• Second trimester. Steady intake matters more than any single day. Observational work links low maternal selenium to pre-eclampsia, gestational diabetes and fetal growth restriction, though these are associations rather than proof that supplementing changes the outcome.
• Third trimester. Requirements rise again after delivery, to 70 mcg a day while breastfeeding. This is the point to look at your total from prenatal plus diet rather than adding a separate selenium capsule on top.

Selenium numbers for pregnancy and breastfeeding