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Monitor for and treat mild hypothyroidism in pregnancy.

PHILADELPHIA -- Physicians should test pregnant women for subclinical hypothyroidism and treat the condition to prevent possible fetal death and developmental abnormalities, according to Dr. Stephanie L. Lee, director of the Endocrine Clinics at Boston Medical Center.

For the first 15 weeks of development, the fetus is dependent on the mother's thyroid hormone. "So if Mom is hypothyroid, then baby is hypothyroid during that critical development period," Dr. Lee said at Endocrinology in the News sponsored by Boston University, INTERNAL MEDICINE NEWS, and FAMILY PRACTICE NEWS.

The risks of fetal loss and impaired development have been borne out in recent studies, she said. For example, a study that looked at the consequences of mild hypothyroidism among pregnant women found that the fetal death rate was four times greater in women with elevated levels of thyroid-stimulating hormone (TSH).

The researchers measured TSH in serum samples taken from women during their second trimester as part of their routine prenatal care. Of 9,403 women with singleton pregnancies, 2.2% (209 women) had TSH levels of 6 mU/L or greater. The rate of fetal death was 3.8% among the women with elevated TSH, compared with 0.9% in women with TSH levels less than 6 mU/L (J. Med. Screen. 2000; 7:127-30).

In another study by the same group of researchers, the results of IQ testing in children born to women who had untreated hypothyroidism during pregnancy were compared with those of children of women who had normal serum thyrotropin levels during pregnancy. Among the children of 48 women with untreated thyroid deficiency during pregnancy, the IQ scores were on average 7 points lower than those of the children of 124 women with normal thyroid levels. In addition, among children of mothers with untreated thyroid deficiency, 19% had IQ scores of 85 or less, compared with 5% of the other children (N. Engl. J. Med. 1999;341:549-55).

These are two bits of information that suggest that maternal hypothyroidism is a very serious condition and needs to be treated and monitored, said Dr. Lee, who had no commercial support to disclose.

Dr. Lee recommends TSH testing as soon as pregnancy is confirmed in women with a strong family history of hypothyroidism, who have a goiter on exam, or who were taking thyroid hormone prior to conception. She advises continuing to monitor these patients every 4-5 weeks through the first 20 weeks of gestation. After 20 weeks, the increased demand from the fetus seems to slow or stop, Dr. Lee said.

"Because these pregnant women do not see their [obstetricians] until week 12 or 13, it really is up to the internist to make sure that they know that they have to get the thyroid levels checked," Dr. Lee said.

The Endocrine Society made similar recommendations in clinical practice guidelines released in 2007. The society advises physicians to measure TSH in women at high risk for thyroid disease.


New York Bureau

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Article Details
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Title Annotation:Women's Health
Author:Schneider, Mary Ellen
Publication:Family Practice News
Article Type:Clinical report
Geographic Code:1USA
Date:Jun 1, 2008
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