Heavy smokers appear to have a reduced chance of conceiving male children, according to a new report by researchers in Japan and Denmark. During the past few decades, the birth ratio of male to female children has declined substantially in a number of developed countries. Although factors underlying this trend are unknown, some scientists have suggested that chronic exposure to environmental toxins may disproportionately affect men and the male reproductive system.
In the study, which was published in the April 20 issue of The Lancet, the researchers recorded the sex of nearly 12 000 liveborn infants (single births). In addition, each mother was asked about her own smoking habits and those of her spouse around the time of conception.
Stephenson J. More Smokes = Fewer Sons?. JAMA. 2002;287(18):2353. doi:10.1001/jama.287.18.2353