Ask An Expert: Thyroid Problem and Pregnancy

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Ask An Expert: Thyroid Problem and Pregnancy

Question:

My 21-year-old daughter is planning to have a baby. She has congenital hypothyroidism, and was placed on medications when she was 10 days old. How will her condition affect a developing fetus?

Answer:

The thyroid gland is a small butterfly-shaped organ located in the neck. The gland regulates the body's metabolism – the rate at which it uses and produces energy – by secreting thyroid hormone. An overactive thyroid gland (hyperthyroidism) can lead to weight loss, fever and jitteriness. An under active thyroid gland (hypothyroidism) is associated with weight gain, hair loss and a feeling of sluggishness.

Rarely (1 in 4,000 births), babies are born without the ability to make thyroid hormone. Untreated, this condition results in health problems including mental retardation. If the condition is recognized early and treated with thyroid hormone replacement, development can be normal. It is for this reason that many states screen all newborns for congenital hypothyroidism.

A mother's thyroid hormone is needed during pregnancy to not only regulate her metabolism but also as a vital ingredient in the normal development of a fetus's brain. Small amounts of maternal thyroid hormone cross the placenta and contribute to the normal development of the fetal nervous system. Women who are being treated with thyroid hormone replacement for hypothyroidism require higher doses of hormone replacement during pregnancy. These women need regular blood tests to assure that they and their babies receive the hormone they need. With careful attention, however, both mother and baby should be healthy.

Most instances of congenital hypothyroidism are sporadic. However, a minority are related to inherited problems. When a sibling or parent has congenital hypothyroidism, special attention should be given to screening subsequent children.

Jeffrey Ecker, M.D. is an Associate Professor of obstetrics, gynecology and reproductive biology at Harvard Medical School and a member of the Department of Obstetrics and Gynecology at Massachusetts General Hospital, where he practices maternal-fetal medicine.

Last updated:	June 15, 2007