Oct. 2, 2000 -- Even if a woman doesn't smoke, just being around a spouse, friend, or co-worker who does could significantly lower her chances of being able to get pregnant.
Many different conditions affect fertility, in both men and women. Smoking lowers a woman's fertility by about 20%, while men who smoke have lower sperm counts by about 16%, some research has shown. So a woman who smokes automatically lowers her fertility potential. But if her partner also smokes, or if she spends time breathing the smoke of others, it may take her much longer than she expected to get pregnant -- or so says a new study by British researchers.
Study author W. Christopher L. Ford, PhD, says a woman who smokes and is exposed to others' smoke can be expected to have the greatest delays in trying to become pregnant. "The passive smoke adds on as though you were smoking more cigarettes yourself," he explains.
In his study, published in the journal Fertility and Sterility, Ford found that women who smoked and had a partner who smoked were significantly less likely than others to become pregnant in six months of trying to conceive. Women smokers also had less success getting pregnant within a year of trying, and the delay increased along with the number of cigarettes smoked per day.
Women who did not smoke but were exposed to passive smoke were more likely than those with no such exposures to be unable to conceive within six months, but they had a higher likelihood of getting pregnant in a year of trying than women who smoked.
Previous studies have shown that chemicals in tobacco smoke can damage a man's sperm and can actually lodge in a woman's ovaries and interfere with her reproductive function. Although Ford's team didn't actually test the ovaries of women who'd been exposed to passive smoke to look for evidence of harmful tobacco byproducts, he says it makes sense that heavy exposure to passive smoke -- and, especially, living with a smoker -- could cause the same problems as actual smoking for women trying to conceive.
"Our advice is, both partners should give up smoking if they are trying to conceive," says Ford. "And also, the woman should avoid exposure to passive smoke, if at all possible."
Based on the majority of the evidence, avoiding passive smoke exposure when you're trying to get pregnant is "a reasonable conclusion," says Brad Van Voorhis, MD, who is associate professor of obstetrics and gynecology at the University of Iowa College of Medicine.
Van Voorhis, who has studied smoking's effect on women undergoing fertility treatments, says the good news is that women who stop smoking seem to be able to get pregnant faster than those who continue. In one study, women having fertility treatments who stopped smoking a month before starting a treatment cycle saw big improvements in their ability to get pregnant -- their fertility rates became similar to those of women who had never smoked. But the longer a woman smoked and the heavier a smoker she was, the harder it became to reverse smoking's effect on her ability to conceive, he says.