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What Are The Normal TSH Ranges During Each Trimester of Pregnancy?


Updated June 02, 2014

Pregnant mixed race woman holding her belly
Peathegee Inc/Blend Images/Getty Images
Updated June 02, 2014
A research article just published this month reported on important information for women with thyroid disease who are thinking about getting pregnant, or who are pregnant.

A summary of key points:

  • Thyroid disorders -- both overt, and sublinical/borderline -- are associated with pregnancy complications and both short- and long-term health implications for both mother and child.
  • The risks are greater for women who have autoimmune thyroid disease, even if the thyroid levels are normal ("euthyroid.")
  • Women with higher TSH levels have a greater than three-fold increase in the risk of very preterm delivery.
  • Pregnant women who test positive for antithyroglobulin antibody (TgAb) when they first start receiving prenatal care have a more than two-fold increased risk of very preterm delivery.
  • Women who are on thyroid hormone replacement should plan to increase their dosage by 30% to 60% during the first few weeks of pregnancy, and ultimately are likely to need to have their thyroid hormone dosage increased by as much as 50% during pregnancy.


According to research, during a normal pregnancy, the following are the TSH normal ranges for an iodine-sufficient population without autoimmune antibodies...
First Trimester: 0.24 - 2.99
Second Trimester: .46-2.95
Third Trimester: .43 - 2.78

For more information on the effects of maternal thyroid dysfunction in pregnancy, see the following selected resources:

Source: Soldin, Offie, "Thyroid Function Testing in Pregnancy and Thyroid Disease: Trimester Specific Reference Interfals," Therapuetic Drug Monitor, Volume 28, No. 1, February 2006

Mary Shomon, About.com's Thyroid Guide since 1997, is a nationally-known patient advocate and best-selling author of 10 books on health, including "The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss," "Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You...That You Need to Know," "Living Well With Graves' Disease and Hyperthyroidism," "Living Well With Autoimmune Disease," "Living Well With Chronic Fatigue Syndrome and Fibromyalgia," and the "Thyroid Guide to Fertility, Pregnancy and Breastfeeding Success." Click here for more information on Mary Shomon.

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