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Cigarette smoke increases the risk of ectopic pregnancy
Last reviewed: 01.07.2025
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Under the influence of nicotine, the wall of the fallopian tubes changes, becoming similar in structure to the wall of the uterus.
Cigarette smoke increases the risk of ectopic pregnancy by reducing the expression of a specific fallopian tube gene called BAD. The discovery was made by scientists Andrew Horne and Colin Duncan of the Medical Research Council at the Centre for Reproductive Health in Edinburgh, UK. It was presented on July 3 at the annual meeting of the European Society of Human Reproduction and Embryology in Istanbul.
An ectopic pregnancy occurs when a fertilized egg implants outside the uterus, most commonly in the fallopian tubes. The incidence of the condition is 2 percent of all pregnancies. It is the most common cause of maternal death in the early stages of pregnancy because the fallopian tube may rupture as the embryo grows, causing massive internal bleeding. Treatment involves surgical removal of the fertilized egg from the tube or injection of methotrexate into it. There is currently no effective way to prevent ectopic pregnancy.
According to Dr. Horn, ectopic pregnancy is the result of a combination of factors that disrupt the transport of the embryo through the fallopian tube to the uterus and changes in the structure of the tube wall, which makes implantation of the egg possible. And the main factor affecting the structure of the fallopian tube wall is smoking. Dr. Horn proved this by influencing the cells of the fallopian tube with a nicotine metabolite, cotinine. It turned out that cotinine reduces the expression of the BAD gene, which regulates cell death (apoptosis). As a result, the wall of the fallopian tube acquires a structure similar to the structure of the uterine wall, so the egg can attach to it.
“We hope that our research will help scientists find ways to prevent ectopic pregnancy, better diagnose it and treat it early in the future,” the study authors believe.
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