New study found pregnant women who undergo dental X-rays face an increased risk of having underweight babies.
The study lacked data on whether babies born to X-ray-exposed mothers developed any 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."
Generally, the academy has told pregnant women that medical and dental X-rays of the head and neck are safe.
Similar findings were reported in babies of women exposed during childhood to radiation for cancer treatment. X-rays tend to involve lower doses, reports thestar.com
According to BBC Dr Hujeol said: "We don't know whether radiation affects neurohormonal mechanisms in the head and neck region, such as thyroid function, or whether factors unrelated to the X-rays are to blame.
"The findings are surprising because the amount of radiation pregnant women were exposed to was very low and generally thought to be incapable of inducing observable health effects.
"The highest dose observed in our study was about the same amount of radiation exposure as flying 16 round-trips from New York to London."
Other studies have shown that different types of diagnostic radiation, such as those used to investigate spine problems, can also associated with low birth weight.
A spokesman for the British Dental Association said: "The risk associated with dental X-rays is very small. "Dentists take X-rays only when they deem it to be necessary as part of diagnosis, and most dentists will be more cautious about performing dental treatments on pregnant women. "Women must tell their dentist if they are pregnant, or even if they think they may be pregnant."