A study in the April 28 issue of The Journal of the American Medical Association that suggested an association between women’s exposure to dental radiographs and low-weight births reinforces the ADA’s long-standing recommendation that patients use both abdominal aprons and thyroid collars, whenever practical, to minimize radiation exposure.
Lead author Philippe Hujoel, Ph.D., of the University of Washington, Seattle, concluded that dental radiography during pregnancy is associated with low-birth-weight babies delivered at full term. Dr. Hujoel hypothesized that low-dose radiation to the mother’s thyroid gland is related, though the study does not establish causality.
"This was a carefully designed retrospective, population-based case-control study," said Dr. Carol Anne Murdoch-Kinch of the ADA Council on Scientific Affairs. "It’s important to note that case-control studies cannot prove cause and effect; they can be used only to demonstrate associations."
Dr. Hujoel also identified several confounding factors. For example, the analysis was limited to women who reported not smoking. However, women may be less likely to report smoking during pregnancy, and smoking is a known risk factor for delivering a low-birth-weight baby and for dental disease.
Researchers also noted that women who need radiographs during pregnancy may have serious dental disease and already may be at risk of having a low-birth-weight baby because of the disease.
"Were these radiographs taken due to an existing oral infection, such as periodontal disease, abscesses or deep caries?" asked Dr. Marjorie K. Jeffcoat, editor of The Journal of the American Dental Association, who has conducted research on low birth weights.
"Certainly, this paper raises some provocative questions, which need to be further explored in well-designed, prospective clinical trials," said Dr. Murdoch-Kinch, also a board-certified diplomate of the American Academy of Oral and Maxillofacial Radiology.
In a statement released to the news media, the ADA recommended that pregnant women should continue to see a dentist regularly for oral examinations and professional teeth cleanings. Maintaining good oral health during pregnancy, noted the Association, can be critical to the overall health of expectant mothers and their babies.
"Left untreated, some maternal oral problems can potentially threaten the health of unborn children," the ADA said. "For example, studies have shown that pregnant women with severe gum disease may be at increased risk for preterm delivery. Preliminary follow-up studies have shown professional oral health care administered during pregnancy to this at-risk group actually improved pregnancy outcomes."
The Association also recommends that pregnant women postpone elective dental radiographs until after delivery. There are, however, times when a radiograph may be required during pregnancy to help dentists diagnose and treat oral disease.
"If the patient is symptomatic, has an infection, or needs immediate treatment, X-rays may be important," says Dr. Jeffcoat, also dean of the University of Pennsylvania dental school.
When dental radiographs are required, the Association recommends that a protective thyroid collar and apron be used, unless specific clinical conditions indicate otherwise.
