According to background information in the article, the link between radiation and low birth weight (LBW) babies has been established with medical x-rays, but not dental x-ray radiation. "Because dental diagnostic radiography results in measurable radiation doses to the hypothalamus-pituitary-thyroid axis and not the reproductive organs or the fetus, it provides an opportunity to test the role of the hypothalamus-pituitary-thyroid axis in the radiation-LBW association," the authors write.

Philippe P. Hujoel, Ph.D., and colleagues from the University of Washington, Seattle, analyzed data from Washington Dental Services, a non-profit dental insurance company in Washington State, for women who received dental treatment between January 1993 and December 2000. Those records were then linked to birth certificates. There were 1,117 low birth weight infants (defined as weighing less than 2,500 grams or 5.5 pounds) born to women with Washington Dental Service insurance during that time period. A total of 4,468 normal birth weight (NBW) infants were selected as the control group for this study.

The investigators estimated the amount of radiation exposure based on the dental x-ray studies performed and published radiation dosages. (For example, a full mouth 21 x-ray series has a typical dose of 1.6 mGy [milligray] of radiation, whereas a series of 4 "bitewing" x-rays has a dose of 0.22 mGy). For their analysis, the authors categorized the cumulative radiation exposure into three dose groups: 0 mGy (no dental x-rays), 0.1-0.4 mGy, and higher than 0.4 mGy (which corresponded to the 90th percentile of the cumulative radiation doses among women who had at least one dental x-ray.)

Among the women who delivered a LBW infant
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JAMA and Archives Journals
27-Apr-2004