Another reason to quit: smoking linked to ectopic pregnancy

Published on Monday 27 September 2010 15:33

A CHEMICAL found in cigarette smoke increases women's risk of suffering a pregnancy which develops outside the womb, Scottish researchers have found.

About one in 50 pregnancies is ectopic, meaning the baby starts to grow before entering the womb, usually in the fallopian tubes.

Now scientists at Edinburgh University have discovered why women who smoke have a higher risk of developing such pregnancies. The Edinburgh team found that female smokers who have had an ectopic pregnancy have raised levels of the protein PROKR1 in their fallopian tubes, increasing the risk of an egg implanting outside the womb.

It is believed a chemical in cigarette smoke called cotinine triggers a chain reaction that increases PROKR1 in the fallopian tubes. While this protein allows the pregnancies to implant correctly inside the womb, its presence in the fallopian tubes is believed to increase the risks of the egg implanting somewhere else.

The study, published in the American Journal of Pathology, found that women who smoked and developed an ectopic pregnancy had double the levels of this protein in their fallopian tubes compared with women who did not smoke and had previously had a healthy pregnancy. Researchers believe too much PROKR1 prevents the muscles in the fallopian tubes from contracting, which then hinders the transfer of the egg to the womb.

Dr Andrew Horne, of the university's Centre for Reproductive Biology, said: "This research provides scientific evidence so 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 blood stream and affect seemingly unconnected parts of the body."

The study, funded by Wellbeing of Women, analysed tissue samples from female smokers and non-smokers, and from women who had previously had ectopic and healthy pregnancies.

Virginia Beckett, spokeswoman for the Royal College of Obstetricians and Gynaecologists, said: "This research strengthens our argument about how important it is to plan pregnancies, and before you start trying for a pregnancy make lifestyle changes which will reduce risks to you and your baby."

Izzie Oakley, from the Ectopic Pregnancy Trust, said: "This research gives those women at risk the opportunity to prevent ectopic pregnancy from cigarette smoking by better understanding the reasons to quit."