Committee on Practice Bulletins—Obstetrics ACOG Practice Bulletin Number 148: Thyroid disease in pregnancy, April 2015. Obstet Gynecol. 2015;125: 996–1005. Full text of ACOG Practice Bulletins is available to ACOG members at www.acog.org/Resources-And-Publications/Practice-Bulletins/Committee-on-...
Thyroid Disease in Pregnancy Uncontrolled thyrotoxicosis and hypothyroidism are associated with adverse pregnancy outcomes. Correspondingly, there is concern about the effect of overt (ie, symptomatic) maternal thyroid disease and even subclinical maternal thyroid disease on fetal development. In addition, medications that affect the maternal thyroid gland can cross the placenta and affect the fetal thyroid gland. This document reviews the thyroid-related pathophysiologic changes that occur during pregnancy and the effects of overt and subclinical maternal thyroid disease on maternal and fetal outcomes.
Used with permission. Copyright the American College of Obstetricians and Gynecologists.
What’s new in thyroid disease in pregnancy in 2015?
By Sarah J. Kilpatrick, MD, PhD
Dr. Kilpatrick is the Helping Hand Endowed Chair, Department of Obstetrics and Gynecology, Cedars-Sinai Medical Center, Los Angeles, California. She is also on the editorial board of Contemporary OB/GYN.
Practice Bulletin 148 published in April of 2015 replaced Practice Bulletin 37 from 2002.1,2 Not surprisingly the basics of thyroid function and its alteration with thyroid disease (hypothyroidism and hyperthyroidism) have not changed in 13 years. Untreated overt hypothyroid or hyperthyroid disease is still harmful for a woman, her pregnancy, and/or her fetus. However, there are some interesting changes in the Practice Bulletin, most of which reflect the ongoing controversy about whether subclinical hypothyroid disease should be a concern in pregnancy, and there are some important affirmations.
Routine screening. The recommendation to not perform routine screening for thyroid disease in pregnancy not only has not changed, it has actually been moved from a Level C recommendation to a Level A recommendation. Remember, Level C recommendations are based on consensus and expert opinion only, whereas Level A recommendations are based on good and consistent scientific evidence. The change is based on 3 facts:
1. Reaffirmation that studies suggesting an association between subclinical hypothyroidism in pregnancy and impaired neurodevelopment in offspring are just that, an association;
2. Publication of new studies with mixed results about putative associations between subclinical hypothyroidism in pregnancy and other adverse outcomes (preterm delivery, preeclampsia, gestational diabetes)3-6; and most importantly
3. Publication of a large randomized trial that showed no difference in cognitive function in 3-year-old children of mothers randomized to screening and treatment versus no treatment for subclinical hypothyroid disease.7
So it is really time to stop screening until we have data that screening and treatment of women with subclinical hypothyroid disease results in improvement in maternal or neonatal outcomes!