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 "We often think of the diseases that secondhand
smoke causes as diseases of older people," epidemiologist Andrew
Hyland told Reuters Health. "The results of this study show that
secondhand smoke can affect even unborn babies."
Hyland led the study at the Roswell Park Cancer Institute in
Buffalo, New York. He and his colleagues found the pregnancy risks
associated with women's secondhand smoke exposure were almost as
high as the risks related to their own cigarette smoking.
The study was the first to investigate the effects of secondhand
smoke using quantified, lifetime exposure levels. The analysis arms
clinicians like Dr. Maurice Druzin, from Stanford University Medical
Center in California, with facts to try to persuade expectant
fathers and others living with pregnant women to refrain from
smoking at home.
"This is excellent ammunition for us to emphasize what we've known
for a long time, but now we've got data to support it," Druzin, who
was not involved in the study, told Reuters Health.
"This is the first study that shows that secondhand smoke has the
same effect as being a primary smoker," he said. "That is a game
changer."
Hyland's team used data from a study of 80,762 women between the
ages of 50 and 79 years old. Researchers asked the women about their
own smoking and the amount of secondhand smoke they were exposed to
as children and adults, as well as about their history of pregnancy
problems.
Among women who never smoked themselves, the chances of having a
stillbirth were 22 percent higher for those who were exposed to any
tobacco smoke than for unexposed women. That was after the
researchers took into account other potential contributors,
including women's weight, education and alcohol drinking.
For women who were exposed to the highest lifelong levels of
secondhand smoke, the risk of having a stillbirth was even greater — 55 percent higher than among unexposed women.
The researchers defined the highest level of exposure to secondhand
smoke as at least 10 years of exposure during childhood, at least 20
years during adulthood and at least 10 years in the workplace.
At that level, a woman's risk of a tubal ectopic pregnancy was 61
percent higher than among unexposed women, and her risk of a
miscarriage was 17 percent higher.
"We're not talking about an elevated risk of a rare event," Hyland
said of the miscarriage finding. "We're talking about something that
happens all the time."
Nearly one third of women in the study reported at least one
miscarriage, 4.4 percent reported at least one stillbirth and 2.5
percent reported at least one tubal ectopic pregnancy, according to
findings published in Tobacco Control.
Ectopic pregnancy occurs when a fertilized egg attaches outside the
uterus, usually in one of the fallopian tubes. Tubal pregnancies are
the leading cause of maternal death during the first trimester of
pregnancy, according to the Centers for Disease Control and
Prevention.
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Researchers cannot draw firm conclusions about cause and effect
from observational studies, like the current one. But the study
results point to the benefits of minimizing exposure to secondhand
smoke, Hyland said.
"There's a biological plausibility that secondhand smoke could
have an impact on these reproductive outcomes not only during the
reproductive years but throughout the lifetime of a woman," he said.
"The take-home message is these never-smoking women who had the
highest levels of exposure to secondhand smoke had the highest
risks," he said. "These risks were generally comparable to the risks
for women who ever actively smoked."
Prior research firmly established that smoking during pregnancy is
associated with a higher risk of fetal death, the authors write.
Smoking during pregnancy also has been linked to infertility,
premature birth, low birth weight, birth defects and sudden infant
death syndrome, they add.
The American Cancer Society estimates that 10 to 15 percent of
women smoke during pregnancy and that as many as 5 percent of infant
deaths could be prevented if pregnant women did not smoke.
Tobacco researcher Stanton Glantz told Reuters Health the current
study adds to a growing body of research suggesting that secondhand
smoke is linked to nearly as many health problems as active smoking.
"The interesting thing is that the passive smoking risks weren't
terribly different from the active smoking risks," said Glantz, from
the University of California, San Francisco. He was not involved in
the new study.
"Even secondhand smoke is giving you enough exposure to trigger
these bad reproductive effects," he said. "If people want to smoke,
they should go outdoors, away from other living things."
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Source: http://bit.ly/1fR7FVr
Tobacco Control, online Feb. 26, 2014.
[© 2014 Thomson Reuters. All rights
reserved.] Copyright 2014 Reuters. All rights reserved. This material may not be published,
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