Markedly low thyroid function, called hypothyroidism, 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 could possibly affect a newborn’s cognitive development and increase the chances for pregnancy and birth complications.
Now, a large, long-term study has found no differences in cognitive functioning among children born to mothers with mildly low hypothyroidism who were treated with medication during pregnancy and children whose mothers were not treated for the condition. The study also found no differences between the groups in rates of preterm birth, stillbirth, miscarriage and gestational diabetes. Similarly, there were no differences in the results of developmental assessments between the two groups of children through age five.
“Our results do not support routine thyroid screening in pregnancy since treatment did not improve maternal or infant outcomes,” said author Uma Reddy, M.D., of the Eunice Kennedy Shriver National Institute of Child Health and Human Development’s Pregnancy and Perinatology Branch, whose study appeared in the New England Journal of Medicine. The study involved researchers at 15 centers in the network and more than 97,000 women.