Levothyroxine Management During Pregnancy

Special Considerations

• The American Medical Association recommends treatment with levothyroxine for subclinical hypothyroidism during pregnancy to restore serum TSH to the reference range 1
• Pregnant women with low T4 and normal TSH should be treated with levothyroxine to restore T4 levels to the normal range, despite normal TSH values, as this pattern may represent isolated maternal hypothyroxinemia, which can have adverse effects on fetal development 2

Preconception Planning

• Women with hypothyroidism should be counseled about the importance of achieving optimal thyroid function before conception, with a target preconception TSH below 1.2 mIU/L 3

Risks of Untreated Hypothyroidism in Pregnancy

• Untreated maternal hypothyroidism increases the risk of preeclampsia, and inadequate treatment is associated with low birth weight in neonates, according to the American Academy of Family Physicians 3
• Maternal hypothyroxinemia has been associated with impaired fetal neuropsychological development 2