Controversies Surrounding Pregnancy, Maternal Thyroid Status, and Fetal Outcome
Abstract
EDITORIAL Controversies Surrounding Pregnancy, Maternal Thyroid Status, and Fetal Outcome Kenneth D. Burman, M.D. N ormal maternal thyroid function during pregnancy is critical for fetal development (1). Deï¬cient maternal thyroid hormone levels during pregnancy are associated with impaired neuropsychological development in childhood, premature birth, preeclampsia, and fetal mortality (2â5). Conversely, excessive maternal thyroid hormone levels have been linked to fetal loss, disturbed fetal growth, preeclampsia, and preterm delivery (1,6). In this issue Hallengren et al. (7) advance our understanding of the risks of perturbed maternal thyroid status. They found that fetal loss occurred in 6% (2 of 32) of levothyroxine-treated hypothyroid women whose serum thyrotropin (TSH) level was normal when initially tested during pregnancy. In contrast, fetal loss occurred in 29% (9 of 31) of women who were otherwise comparable except that their TSH level was abnormal. In this study TSH and other thyroid tests were performed at 3 to 13 weeks of gestation (mean ¼ 8.5 weeks) and their levothyroxine dose was adjusted in the second or third trimester. Among the many controversies surrounding pregnancy, maternal thyroid status, and fetal outcome, one of the most contentious is whether thyroid function screening should be performed in all pregnant