There are many risk factors for endometriosis, the painful condition in which tissue similar to that lining your uterus grows outside that organ. One risk factor may be smoking tobacco products. However, evidence on the connection between smoking and endometriosis has been mixed.

A closer look at the research reveals that your personal smoking habits may not increase your risk of endometriosis. But some findings do support a connection between smoking and endometriosis during infant and childhood development. One study reported a pregnant mother’s exposure to someone else’s smoke (aka secondhand smoke, sometimes called passive smoking) can increase their child’s risk of developing endometriosis later in life. Here we explore what’s known — and what’s inconclusive — about the relationship between cigarette smoking, smoke exposure, and endometriosis.

Smoking and Endometriosis: What Does the Research Say?

Studies surrounding the topic of smoking cigarettes and endometriosis have yielded mixed findings. Some show an association between smoking and endometriosis, while others don’t.

What Scientific Literature Says on the Whole

One way to spot trends in the findings of a large number of different studies is with a meta-analysis. Using statistics, a meta-analysis compares multiple published reports, papers, and more. This gives an overall snapshot of what scientific literature as a whole says about a certain topic.

In 2014, a meta-analysis of 38 papers related to endometriosis was conducted by a team of Italian scientists. Within those papers, the scientists were able to compare the more than 13,000 people — nonsmokers and smokers — studied, all of whom were diagnosed with endometriosis.

The studies reviewed in the meta-analysis were a mixed bag. Some found smoking had no effect on participants’ risk for endometriosis. Others found that smoking increased participants’ risk of endometriosis. Still others found that smoking decreased participants’ risk of endometriosis. In the end, the meta-analysis team determined there was no meaningful association that could be made between smoking and a person’s risk of endometriosis.

What Individual Reports Find

While scientific literature on the whole does not seem to support an association between smoking and endometriosis, some individual studies tell a different story.

One such “different story” focused on 90 people with endometriosis and 90 people without the condition, all of whom were seeking treatment at a fertility clinic. The researchers found that factors like a person’s menstrual cycle — its regularity and length — and their use of birth control and/or alcohol were not significantly related to endometriosis. However, when the researchers studying those 180 participants looked at their smoking habits, interesting patterns appeared.

If a participant had never given birth but had always smoked (called an “ever smoker”), researchers found they were more likely to have endometriosis. However, the same connection could not be made for participants who were ever smokers and had given birth. The researchers concluded that previous meta-analyses had not taken a person’s history of childbirth into account.

The study also showed there was no correlation that could be made between people who currently smoked and their risk of endometriosis. However, that might be because the study’s participants were being treated at a fertility clinic and had been told to quit smoking. (Such advice to abstain comes from the well-documented effects of smoking on infertility.)

Another study, this one out of Korea and published in 2021, examined more than two million siblings. In it, scientists tried to assess family patterns between smoking and a person’s risk of developing endometriosis. The researchers found that people who smoked and had a family history of endometriosis ran a significantly higher risk of the condition when compared to the general population. These findings suggest that inherited genetic factors may combine with environmental factors (such as smoking) to lead a person to develop endometriosis.

Secondhand Smoke and Endometriosis

Encountering secondhand smoke while you were in the womb might factor into your risk for endometriosis. Some research shows that if a pregnant person smokes while carrying their baby, that child has a greater chance of eventually developing endometriosis.

Not all research supports this finding, though. One 2020 meta-analysis of 11 published studies looked for links between a participant’s endometriosis diagnosis and if their birth parent smoked. It also analyzed if the participants were later exposed to secondhand smoke as a child. The meta results were mixed. Of those papers reviewed, one found some association between smoking and endometriosis, three found no association, and one showed that secondhand smoke exposure decreased a person’s risk.

The Bottom Line

Altogether, these studies show that the causes and risk factors of endometriosis (especially with respect to smoking) need to be better understood.

While it’s unclear whether smoking or exposure to smoking may contribute to endometriosis, there are many other proven reasons you are better off avoiding smoking and passive smoking. Foremost is the associated cancer risk. Also, smokers may be at more risk of developing heart disease. (Remember: Heart disease is already a potential risk for people with endometriosis.)

If you smoke, talk to your doctor to better understand its risks to you and others, and for help finding ways to quit when you’re ready.

Talk With Others Who Understand

On MyEndometriosisTeam, the social network for people with endometriosis and their loved ones, more than 123,000 members come together to ask questions, give advice, and share their stories of living with endometriosis with others who understand.

Are you concerned about smoking, secondhand smoke, and endometriosis? Have experience to impart? Share your experience in the comments below, or start a discussion on MyEndometriosisTeam.