Hypothyroidism During Pregnancy (Thyroid Deficiency During Pregnancy)

  • Medical Author:
    Ruchi Mathur, MD, FRCP(C)

    Ruchi Mathur, MD, FRCP(C) is an Attending Physician with the Division of Endocrinology, Diabetes and Metabolism and Associate Director of Clinical Research, Recruitment and Phenotyping with the Center for Androgen Related Disorders, Department of Obstetrics and Gynecology at Cedars-Sinai Medical Center.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

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Quick GuideThyroid Problems Explained

Thyroid Problems Explained

How is hypothyroidism treated during pregnancy?

In many respects, the treatment of hypothyroidism in pregnant women is similar to that in nonpregnant women.. A synthetic form of T4 is given to replace the missing hormone. The medication dose is regularly adjusted to maintain a steady blood level of thyroid hormone within the normal range. Therefore, it is routine practice to monitor the blood level of the thyroid stimulating hormone (TSH) during pregnancy. For more information, please read the article on Hypothyroidism.

What are the consequences of hypothyroidism during pregnancy?

For years, physicians have known of a link between mothers with hypothyroidism during pregnancy and developmental delay in their children after birth. This was particularly seen in mothers who came from iodine deficient areas of the country (iodine is necessary to produce thyroid hormone and is now a common component of the salt in our foods) and was also observed in mothers with autoimmune thyroid disease, such as Hashimoto's thyroiditis.

There is a relationship between thyroid levels in the mother and brain development of her child. A large study reported in 1999 found that undetected or inadequately treated hypothyroidism in mothers was associated with IQ changes in the infants of these women. The average IQ scores were about 4 points lower in the children of hypothyroid mothers than in children of normal mothers. Larger IQ deficits were seen in the children of mothers who had more severe hypothyroidism. These children had an average IQ 7 points lower than normal. In addition, almost 20% of these children had IQ scores of less than 85 compared to 5% of the children of normal mothers. The children of hypothyroid mothers were also more likely to have difficulty in school or have repeated grades.

This study demonstrates that uncontrolled hypothyroidism in pregnant women can have long-term effects on the children of these mothers. Also, the effects occur even if the hypothyroidism is mild and the woman does not exhibit any symptoms. However, the more significant the hypothyroidism, the greater the likelihood of developmental problems.

Medically Reviewed by a Doctor on 2/3/2016

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