UW study links dental X-rays to smaller babies

By Lindsey Tanner
The Associated Press

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The study lacked data on whether babies born to X-ray-exposed mothers developed problems associated with low birth weight, including lung ailments and delays in physical or mental growth.

Still, Dr. Michael Fleming, president of the American Academy of Family Physicians, called the study "potentially very significant because it really changes the information that we've believed all these years."

While doctors and dentists usually are cautious about performing X-rays on pregnant women, the academy has told pregnant women that medical and dental X-rays are safe.

Fleming said the study will "make us take a closer look at the data."

The study, which appears in today's Journal of the American Medical Association, involved about 4,500 women who gave birth while enrolled in a dental-insurance plan in Washington state between 1993 and 2000.

A total of 1,117 low-birth-weight babies, those weighing less than 5 pounds, 8 ounces, were born to study participants. Women who had had dental X-rays during pregnancy faced about double the risk of having a low-birth-weight baby born either prematurely or full-term, and more than triple the risk of having a full-term underweight baby.

There was no link found between X-rays and the smallest babies, those born at less than 3 pounds, 4 ounces.

All the women who had dental X-rays had them during the first trimester, when they might not have known they were pregnant.

The study's lead author, Dr. Philippe Hujoel, a professor of dental public-health services at the UW, said more research is needed to determine if dental X-rays were the culprit.

Hujoel said it is unclear how dental X-rays might affect fetuses but theorized the radiation might cause subtle changes in the functioning of the mother's thyroid gland, in the neck.
 
Previous studies have found an increased risk of low-birth-weight babies in women with mild thyroid disease, he said.

The researchers lacked information on why the women received X-rays. Hujoel said that although the X-rays were probably for routine checkups, they might have been prompted by conditions that could increase the risk of low-birth-weight babies.

In the meantime, Hujoel said, the results should not discourage pregnant women with dental emergencies such as toothaches from seeking appropriate care, including X-rays.

The risks of such problems might outweigh any dangers from the X-rays, he said.

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