Drs. Andrew Horne and Colin Duncan of the Medical Research Council Centre for Reproductive Health in Edinburgh, Scotland, said ectopic pregnancy -- when the embryo implants in the Fallopian tube -- is the most common cause of maternal death in early pregnancy.
Ectopic pregnancy occurs in up to 2 percent of all pregnancies.There is no way to prevent the condition, which must be treated by abdominal surgery or, if the ectopic is small and stable, by injection of a drug called methotrexate.
Horne and colleagues exposed cells from the Fallopian tube to a breakdown product of nicotine -- cotinine. They then showed that cotinine had a negative effect on genes known to be associated with cell death, or apoptosis, and in particular with a particular gene.
In a further study the researchers showed that the gene's reduced production in the Fallopian tube of women who were smokers.
"The research is exciting because it provides new scientific evidence to help understand why women who smoke are more likely to have ectopic pregnancies," Horne said. "It appears that smoking reduces the production of genes, which are involved in the control of cell death and promote an environment in the Fallopian tube which is attractive to the developing embryo."
The findings were presented at the European Society of Human Reproduction and Embryology in Istanbul, Turkey.