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Levothyroxine Pregnancy and Breastfeeding Warnings

Levothyroxine is also known as: Eltroxin, Euthyrox, Eutroxsig, Evotrox, L Thyroxine Roche, Levo-T, Levotabs, Levotec, Levothroid, Levothyrox, Levoxyl, Novothyrox, Oroxine, Synthroid, Tirosint, Tirosint-Sol, Unithroid

Medically reviewed by Drugs.com. Last updated on Jul 31, 2019.

Levothyroxine Pregnancy Warnings

Use is considered acceptable

AU TGA pregnancy category: A
US FDA pregnancy category: Not Assigned

Risk Summary: No increased rates of major birth defects or miscarriages have been reported with use during pregnancy; untreated hypothyroidism during pregnancy is associated with risks to the mother and fetus

Comments:
-Thyroid replacement therapy should not be discontinued during pregnancy; hypothyroidism diagnosed during pregnancy should be promptly treated.
-Monitor TSH levels and adjust doses as needed.

Animal studies have not been conducted. There is a long history of using this drug in pregnant women and this experience has not shown increased rates of fetal malformations, miscarriages or other adverse maternal or fetal outcomes. Hypothyroidism during pregnancy is associated with a higher rate of complications, including spontaneous abortion, pre-eclampsia, stillbirth and premature delivery. Maternal hypothyroidism may have an adverse effect on fetal neurocognitive development. Pregnant women taking this drug should have their TSH measured during each trimester and dose adjusted as appropriate. Patients will generally return to their pre-pregnancy dose after delivery. There are no controlled data in human pregnancy.

AU TGA pregnancy category A: Drugs which have been taken by a large number of pregnant women and women of childbearing age without any proven increase in the frequency of malformations or other direct or indirect harmful effects on the fetus having been observed.

US FDA pregnancy category Not Assigned: The US FDA has amended the pregnancy labeling rule for prescription drug products to require labeling that includes a summary of risk, a discussion of the data supporting that summary, and relevant information to help health care providers make prescribing decisions and counsel women about the use of drugs during pregnancy. Pregnancy categories A, B, C, D, and X are being phased out.

See references

Levothyroxine Breastfeeding Warnings

Use is considered acceptable

Excreted into human milk: Yes

Comments:
-Levothyroxine (T4) is a normal component of human milk; limited data on exogenous replacement doses during breastfeeding have not shown an adverse effect in nursing infants.
-Levothyroxine dose requirements may be increased in the postpartum period compared to prepregnancy requirements in patients with Hashimoto's thyroiditis.
-The presence of thyroid hormone in breast milk does not appear to interfere with neonatal thyroid screening.

See references

References for pregnancy information

  1. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. Available from: URL: http://www.appco.com.au/appguide/default.asp." ([2006]):
  2. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical, Abbott Park, IL.
  3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

References for breastfeeding information

  1. Pharmaceutical Society of Australia "APPGuide online. Australian prescription products guide online. Available from: URL: http://www.appco.com.au/appguide/default.asp." ([2006]):
  2. Moller B, Bjorkhem I, Falk O, Lantto O, Lafsson A "Identification of thyroxine in human breast milk by gas chromatography-mass spectrometry." J Clin Endocrinol Metab 56 (1983): 30-4
  3. "Product Information. Synthroid (levothyroxine)." Abbott Pharmaceutical, Abbott Park, IL.
  4. Mizuta H, Amino N, Ichihara K, et al. "Thyroid hormones in human milk and their influence on thyroid function of breast-fed babies." Pediatr Res 17 (1983): 468-71
  5. Jansson L, Ivarsson S, Larsson I, Ekman R "Tri-iodothyronine and thyroxine in human milk." Acta Paediatr Scand 72 (1983): 703-5
  6. Hahn HB, Spiekerman AM, Otto R, Hossalla DE "Thyroid function tests in neonates fed human milk." Am J Dis Child 137 (1983): 220-2
  7. United States National Library of Medicine "Toxnet. Toxicology Data Network. Available from: URL: http://toxnet.nlm.nih.gov/cgi-bin/sis/htmlgen?LACT." ([cited 2013 -]):
  8. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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