Can I take levothyroxine while pregnant or breastfeeding?

8.1 Pregnancy Risk Summary The clinical experience, including data from postmarketing studies, in pregnant women treated with oral levothyroxine to maintain euthyroid state have not reported increased rates of major birth defects, miscarriages, or other adverse maternal or fetal outcomes. There are risks to the mother and fetus associated with untreated hypothyroidism in pregnancy. Since TSH levels may increase during pregnancy, TSH should be monitored and levothyroxine sodium dosage adjusted during pregnancy (see Clinical Considerations) . Animal reproductive studies have not been conducted with levothyroxine sodium. Levothyroxine sodium should not be discontinued during pregnancy and hypothyroidism diagnosed during pregnancy should be promptly treated. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

Prescribing label, section “8.1 Pregnancy” (opening excerpt): Levothyroxine sodium (oral), REMEDYREPACK INC. Read the full section on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.

Levothyroxine (T4) is a normal component of human milk. Limited data on exogenous replacement doses of levothyroxine during breastfeeding indicate no adverse effects in infants. The American Thyroid Association recommends that subclinical and overt hypothyroidism should be treated with levothyroxine in lactating women seeking to breastfeed.[1] Adequate levothyroxine treatment during lactation may normalize milk production in hypothyroid lactating mothers with low milk supply, but does not return milk lipids to normal. Mothers taking levothyroxine because of gestational hypothyroidism may have lower exclusive breastfeeding rates rates at 1 month and increased early formula supplementation.[2] Levothyroxine dosage requirement may be increased in the postpartum period compared to prepregnancy requirements in patients with Hashimoto’s thyroiditis.[3]

“Summary of Use during Lactation”, LactMed record “Levothyroxine” (LM158), quoted verbatim. Everything LactMed reports about Levothyroxine while breastfeeding.

8.2 Lactation Risk Summary Published studies report that levothyroxine is present in human milk following the administration of oral levothyroxine. No adverse effects on the breastfed infant have been reported and there is no information on the effects of levothyroxine on milk production. Adequate levothyroxine treatment during lactation may normalize milk production in hypothyroid lactating mothers with low milk supply. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for levothyroxine sodium and any potential adverse effects on the breastfed infant from levothyroxine sodium or from the underlying maternal condition

Prescribing label, section “8.2 Lactation”: Levothyroxine sodium (oral), REMEDYREPACK INC. Label on DailyMed. Quoted verbatim; US labels are written for US prescribers and patients.