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Your article suggests that somehow X rays caused low-birth-weight babies in women who had their teeth X-rayed during their pregnancies. Here is an alternative possibility: Perhaps unhealthy people are more likely to have low-birth-weight babies and bad teeth.

Stephen Wood
Orlando, FL.

The article hypothesizes that the dental X-rays hitting the thyroid glands of pregnant women affect birth outcomes. This tentative conclusion was reached without evaluating the thyroid glands of the affected mothers or the controls and therefore seems premature. The mothers who went to the dentist and had X rays were more likely, I would guess, to have had dental work done than the controls and would therefore be more likely to have been exposed to anesthesia and dental amalgams, which are about half mercury. Amalgam has been determined unacceptable in Canada and some European countries, particularly for pregnant women. The researchers in this case have failed to evaluate a significant risk factor for the population.

Eric Wolf
Santa Fe, N.M.