1. Stages of Pregnancy Slideshow Pictures
2. Slideshow of Early Pregnancy Symptoms
3. Early Pregnancy Symptoms Quiz

Medical Author:

Ruchi Mathur, MD, FRCP(C)

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.

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Medical Editor:

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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In this Article

• Introduction
• What is the thyroid gland?
• What happens with thyroid disease?
• How is hypothyroidism treated during pregnancy?
• What are the consequences of hypothyroidism during pregnancy?
• How early does the mother's thyroid hormone affect the unborn baby?
• What can be done to avoid the consequences of hypothyroidism in pregnancy?
• Hypothyroidism During Pregnancy At A Glance
• Patient Comments: Hypothyroidism During Pregnancy - Symptoms
• Patient Comments: Hypothyroidism During Pregnancy - Diagnosis
• Find a local Obstetrician-Gynecologist in your town
• Hypothyroidism During Pregnancy Index

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.

Before birth a baby is entirely dependent on the mother for thyroid hormone until the baby's own thyroid gland can start to function. This usually does not occur until about 12 weeks of gestation (the end of the first trimester of pregnancy). Thus, hypothyroidism of the mother may play a role early on, before many women realize they are pregnant! In fact, the babies of mothers who were hypothyroid in the first part of pregnancy, then adequately treated, exhibited slower motor development than the babies of normal mothers. However, during the later part of pregnancy, hypothyroidism in the mother can also have adverse effects on the baby, as pointed out by the research described above. These children are more likely to have intellectual impairment.