Smokers increase their risks of having an ectopic pregnancy by up to four times, according to research.
The University of Edinburgh study, which was funded by the Wellbeing of Women charity, linked smoking to a protein that is thought to increase the chances of an ectopic pregnancy.
Eccyesis is a condition that affects up to 30,000 women in Britain every year, and is caused by a fertilised egg being implanted outside the womb - usually in the fallopian tubes.
In the research, which examined tissue from female smokers and non-smokers, it was discovered that a chemical in cigarette smoke called cotinine increases the levels of a PROKR1 protein in the fallopian tubes.
This protein is believed to prevent the walls of the fallopian tube from contracting, therefore making it more likely for an ectopic pregnancy to occur.
Dr Andrew Horne, from the university’s Centre for Reproductive Biology, said: “This research provides scientific evidence so that we can understand why women who smoke are more at risk of ectopic pregnancies and how smoking impacts on reproductive health.
“While it may be easy to understand why inhalation of smoke affects the lungs, this shows that components of cigarette smoke also enter the bloodstream and affect seemingly unconnected parts of the body like the reproductive tract.”