Smoking parents produce fewer boys
http://www.newscientist.com/news/print.jsp?id=ns99992187
00:01 19 April 02
James Randerson
Parents who smoke produce fewer boys, according to research on Japanese couples. The researchers do not know the mechanism for the effect, but they say both the mother's and father's smoking habits are important.
Stress, temperature, birth order and even the number of wives in a man's harem are all known to influence the relative proportions of girls and boys at birth. But this is the first time birth sex ratio and smoking have been linked.
The researchers questioned over 5000 Japanese women on their smoking habits and those of their partner around the time they conceived their children. The 11,815 births reported were then split into groups based on parental smoking habits and the team compared the ratio of boys to girls in each category.
If neither parent smoked, boys made up about 55 per cent of births. But if both mum and dad were puffing over 20 cigarettes a day this dropped to 45 per cent.. Even if just the father was a light smoker, the proportion of boys was lower.
Weaker sperm
"We cannot say where the effect is," says research team member Anne Byskov at the University Hospital of Copenhagen, Denmark. But she speculates that Y bearing sperm or male foetuses or both are more sensitive to the effects of cigarette smoke.
Previous research has shown differences between X and Y carrying sperm, says Alexander Lerchl at the International University Bremen, Germany: "Y bearing sperm may be a bit faster swimming, but not as long lasting". This might suggest that Y carriers are less robust, but he warns the evidence is only weak.
The study does not attempt to account for other factors such as diet and stress levels that might correlate with smoking. Lerchl says we know that smokers take more health risks and that these factors must be ruled out.
Journal reference: The Lancet (vol 359, p 1407)
00:01 19 April 02
Return to news story
© Copyright Reed Business Information Ltd.
http://www.newscientist.com/news/print.jsp?id=ns99992187
00:01 19 April 02
James Randerson
Parents who smoke produce fewer boys, according to research on Japanese couples. The researchers do not know the mechanism for the effect, but they say both the mother's and father's smoking habits are important.
Stress, temperature, birth order and even the number of wives in a man's harem are all known to influence the relative proportions of girls and boys at birth. But this is the first time birth sex ratio and smoking have been linked.
The researchers questioned over 5000 Japanese women on their smoking habits and those of their partner around the time they conceived their children. The 11,815 births reported were then split into groups based on parental smoking habits and the team compared the ratio of boys to girls in each category.
If neither parent smoked, boys made up about 55 per cent of births. But if both mum and dad were puffing over 20 cigarettes a day this dropped to 45 per cent.. Even if just the father was a light smoker, the proportion of boys was lower.
Weaker sperm
"We cannot say where the effect is," says research team member Anne Byskov at the University Hospital of Copenhagen, Denmark. But she speculates that Y bearing sperm or male foetuses or both are more sensitive to the effects of cigarette smoke.
Previous research has shown differences between X and Y carrying sperm, says Alexander Lerchl at the International University Bremen, Germany: "Y bearing sperm may be a bit faster swimming, but not as long lasting". This might suggest that Y carriers are less robust, but he warns the evidence is only weak.
The study does not attempt to account for other factors such as diet and stress levels that might correlate with smoking. Lerchl says we know that smokers take more health risks and that these factors must be ruled out.
Journal reference: The Lancet (vol 359, p 1407)
00:01 19 April 02
Return to news story
© Copyright Reed Business Information Ltd.
