CHICAGO (Reuters) -
Pregnant women who undergo dental
X-rays may raise their risk of having low birth-weight babies,
researchers said on Tuesday.
The association could be related
to exposing the mothers' thyroid, pituitary or hypothalamus
glands to radiation, even early in the pregnancy.
"Up until now, people assumed that
head and neck radiation will not have any adverse effects on
pregnant women. They assumed that only direct radiation to the
uterus or the fetus would be associated with adverse pregnancy
outcomes," said Philippe Hujoel of the University of Washington in
Seattle, who led the study.
But a seven-year review of a dental
insurance company's records in the state of Washington found
pregnant women who underwent extensive dental X-rays were at three
times the risk of having a low birth-weight baby, characterized as
weighing 5.5 pounds (2.5 kg) or less.
Some 20 percent of the 5,585 infants
in the study had low birth weight.
The study, published in the Journal
of the American Medical Association (news
web sites), divided women into three groups, with the highest
level of radiation exposure from dental X-rays comparable to that
received in four to 16 round-trip flights between New York and
"Since women may not always be aware
of their pregnancy status, it may not be possible to eliminate all
dental radiography during pregnancy, but if this goal could be
achieved and if the identified association is causal, the prevalence
of (term low birth-weight) infants could be reduced by up to 5
percent," the report said.