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When men smoke while their partners are pregnant, their daughters may end up reaching menopause about a year earlier, a new study suggests.
Previous research has found that a woman's own smoking habits, as well her partner's, may also precipitate the point at which she can no longer get pregnant.
"It seems that the effect of paternal smoking on a daughter's reproductive life span is stronger than that of (her) husband smoking," study researcher Dr Misao Fukuda, of the M&K Health Institute in Ako, Japan, told Reuters Health in an email.
Smoking affects sperm cells
Fukuda said it's possible that smoke exposure around the time of conception could affect the fertilising capacity of sperm cells and/or the beginning of early embryogenesis.
The researchers questioned more than 1,000 post-menopausal Japanese women who were visiting clinics for gynaecologic exams. They asked the women how old they were at menarche and menopause, as well as whether they or their husbands smoked.
The researchers also asked women if their own mothers or fathers had smoked while the mothers were pregnant.
About three-quarters of fathers had smoked while their daughters were in utero, just as three-quarters of women said their husbands smoked before they reached menopause. Far fewer women in both generations - between 4% and 6% - had smoked themselves while pregnant, or during the time they could have become pregnant.
Overall, the mean age at menopause was 51.
Earlier menopause for smokers
Women who were smokers reached menopause on average about 14 months earlier than women who didn't smoke. When their husbands smoked, they went through menopause five months earlier - but the results were not statistically significant.
Women whose fathers smoked while they were in the womb, stopped having their periods about 13 months earlier than those whose fathers were non-smokers, Dr. Fukuda and colleagues report in Fertility and Sterility. Smoking by fathers didn't influence the timing of menarche, however.
Not enough mothers smoked for the researchers to determine how that influenced their daughters' puberty or menopause.
And the researchers couldn't be sure, based on this study, that the effect of a father's smoking happened before their daughters were born, and not when they were kids.
"The whole issue of teasing apart prenatal effects versus childhood (effects) is really hard to do," said Dr. Jennifer Ferris, who has studied the link between second-hand smoke and puberty at Columbia University, but was not involved in the current study.
Smoke exposure
"Most of the time, if the woman smokes when she's pregnant or the father smokes when she's pregnant, that child will also be exposed to smoking during childhood," she told Reuters Health.
In addition to the effect on sperm cells suggested by Fukuda, Ferris said that chemicals from cigarette smoke may alter glands in the brain that produce reproductive hormones.
She said that more research was needed to explain the link between second-hand smoke and reproduction.
Most women know now that it's dangerous to smoke during pregnancy, Ferris said. However, she added, "It would be nice to see more studies looking at paternal smoking, because that still may be more common than women smoking during pregnancy." - (Genevra Pittman/Reuters Health, June 2011)
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