College of Medicine & Veterinary Medicine

Study pinpoints ectopic smoke link

Scientists have discovered why women who smoke have a higher risk of developing ectopic pregnancies.

Researchers have found that female smokers who have an ectopic pregnancy have raised levels of a protein - called PROKR1 - in their Fallopian tubes, which increases the risk of an egg implanting outside the womb.

The team at the University believe that a chemical in cigarette smoke - called cotinine - triggers a chain reaction that increases PROKR1 levels in the Fallopian tubes.

Around one in 50 pregnancies in the western world is ectopic, with over 300,000 ectopic pregnancies in the UK each year.

Smoker’s risk

The PROKR1 protein allows pregnancies to implant correctly inside the womb.

But if found in the Fallopian tubes, PROKR1 is believed to prevent the muscles in the tube walls from contracting, hindering the transfer of the egg to the womb.

The study found that women who smoked and developed ectopic pregnancy had double the levels of this protein in their Fallopian tubes compared to non-smokers who had previously had a healthy pregnancy.

While it may be easy to understand why inhalation of smoke the lungs, this shows that components of cigarette smoke also enter the blood stream and affect seemingly unconnected parts of the body like the reproductive tract.

Dr Andrew HorneClinical Scientist at the University’s Reproductive Developmental Sciences Division

Maternal mortality

Ectopic pregnancy is the leading cause of maternal mortality in the first three months of pregnancy and leads to fertility problems in the future.

In 98 percent of cases, the egg implants in the Fallopian tube, causing the tube to rupture and resulting in internal bleeding.

This research is published in the American Journal of Pathology.

It was funded by Wellbeing of Women.