March 1, 2017 – A large national study suggests that treating pregnant women for mildly low thyroid function does not improve the IQs of their babies or reduce preterm births or other negative outcomes. The 10-year study, conducted at UT Southwestern Medical Center and 14 other universities and medical centers in the National Institutes of Health’s Maternal Fetal Medicine Units Network, found no benefit in treating the women during their pregnancies.