There appears to be no benefit to treating mildly low thyroid function during pregnancy, according to a study by a National Institutes of Health research network.
Markedly low thyroid function during pregnancy has long been associated with impaired fetal neurological development and increased risk for preterm birth and miscarriage. Similarly, some studies have indicated that even mildly low thyroid function (subclinical hypothyroidism) could possibly affect a newborn’s cognitive development and increase the chances for pregnancy and birth complications. Read more here.