The harmful effect of tobacco on human reproduction

The harmful effects of tobacco on human reproduction

Among the first topics Dr. Miron wanted to cover on our blog was the importance of discussing the harmful effects of tobacco on human reproduction. As a team, we feel it is crucial to address this issue, particularly for our patients who smoke. We frequently encourage them to quit for the sake of their reproductive health.

Smoking and reproductive health: the statistics

According to Statistics Canada, approximately 20–25% of people of reproductive age smoke daily. In Quebec, despite years of awareness campaigns and government initiatives, the rate of smoking cessation has plateaued compared to a decade ago. The “Institut national de santé publique” reports that the smoking rate in Quebec has stabilized at around 23%, which translates to over 1.5 million smokers. Quebec women tend to smoke more than other Canadian women, and nearly 10% of non-smoking Quebec women live with a smoker, exposing them to secondhand smoke and its detrimental effects on fertility.

Tobacco contains over 4,000 compounds, many of which are known for their toxicity. Its harmful impact on human reproduction is well established, affecting both male and female reproductive systems in multiple ways.

The overlooked impact of smoking on fertility

Due to a lack of awareness, many people underestimate how smoking affects fertility. Only 47% of infertile couples and 14% of pregnant women believe that smoking significantly impairs fertility. Moreover, too few healthcare professionals address this issue—only 30% of doctors discuss smoking cessation with their patients struggling to conceive.

Yet, smoking is clearly linked to multiple reproductive health issues, including early menopause, higher infertility risk, and lower success rates with assisted reproduction. Increased risks of miscarriage, ectopic pregnancy, perinatal morbidity, and mortality are also well documented.

Effects of smoking on female fertility

Impact on ovulation

Ovulation is a complex process regulated by hormonal signals. Smoking disrupts this process, accelerating menopause by 2–4 years. Smokers have 66% higher levels of follicle-stimulating hormone (FSH), which typically rises as ovarian reserve declines.

Studies show that smokers have fewer antral follicles and lower levels of anti-Müllerian hormone (AMH), both key indicators of ovarian reserve. The presence of toxic compounds such as nicotine, cotinine, benzopyrene, and cadmium in follicular fluid leads to poorer egg quality, higher rates of chromosomal abnormalities, and DNA damage.

During in vitro fertilization (IVF), smokers require higher doses of medication to stimulate ovulation, have longer treatment cycles, lower estrogen levels, and produce fewer eggs.

Impact on the Fallopian tubes

Proper function of the fallopian tubes is essential for transporting the fertilized egg to the uterus. Tobacco toxins impair this process by altering smooth muscle contractions and reducing the frequency of ciliary movement. Women who smoke more than 20 cigarettes per day are four times more likely to experience an ectopic pregnancy, where the embryo implants outside the uterus.

Impact on fertilization and embryo development

Smoking is associated with delayed conception, increased oxidative stress, and chromosomal instability in embryos. It reduces the likelihood of fertilization and hinders embryonic development, decreasing the chances of an embryo reaching the blastocyst stage (5–6 days old). Smokers undergoing IVF have lower fertilization rates and require twice as many treatment cycles to conceive. Even exposure to secondhand smoke reduces the chances of success in assisted reproduction.

Impact on embryo implantation

For pregnancy to occur, the embryo must successfully implant in the uterine lining (endometrium). Smoking negatively affects endometrial receptivity, reducing implantation rates in smokers (26%) compared to non-smokers (32%). Histopathological studies reveal placental abnormalities as early as the first trimester, along with compromised uterine blood flow and muscle activity. These effects contribute to higher risks of miscarriage, preterm labor, fetal growth restriction, placenta previa, placental abruption, and sudden infant death syndrome (SIDS).

Effects of smoking on male fertility

Tobacco chemicals also harm male reproductive health. Male smoking significantly prolongs the time needed to conceive, yet its impact is often underestimated.

Impact on sperm quality

Smoking leads to a significant decrease in sperm count, semen volume, and sperm motility while increasing white blood cell concentration in semen. The difference between smokers and non-smokers ranges from 20% to 48%.

Additionally, tobacco’s genotoxic effects have been well documented. DNA integrity and nuclear maturation in sperm cells are compromised, leading to higher rates of chromosomal abnormalities. The good news? Quitting smoking can rapidly improve sperm quality—within three months, sperm concentration and vitality show significant improvement.

Biochemical effects on semen

Smokers exhibit an imbalance between oxidative stress markers (such as free radicals) and antioxidant molecules in semen. Toxic compounds like cadmium, lead, and malondialdehyde are elevated, while key antioxidants such as vitamin C, vitamin E, and glutathione-S transferase activity are significantly reduced.

Impact on fertilization

Male smoking reduces IVF success rates by over 40% and decreases the likelihood of a pregnancy progressing beyond the 12th week. Even smoking as little as four cigarettes per day for two years significantly impairs sperm’s ability to fertilize an egg. Secondhand smoke also negatively impacts female partners, reducing the number of eggs retrieved during IVF.

The impact of smoking on offspring

Maternal smoking

Maternal smoking is strongly associated with a higher incidence of birth defects, including heart defects, skeletal malformations (such as missing or extra fingers, clubfoot), cranial bone fusion defects, facial anomalies (such as cleft lip/palate), digestive tract abnormalities, and undescended testes. These congenital anomalies have lifelong physical and psychological consequences for affected children and their families. The financial burden is immense, costing over $2 billion annually in the United States alone.

Maternal smoking also reduces the future fertility of offspring. Studies show a strong correlation between prenatal tobacco exposure and lower sperm counts in male children, as well as reduced fertility in female offspring.

Paternal smoking

In men, tobacco exposure leads to genetic mutations in sperm-producing stem cells. These mutations accumulate over time and may increase the risk of genetic disorders in future generations. Research confirms a link between paternal smoking and childhood cancers.

The impact of cannabis on fertility

Like tobacco, cannabis also has harmful effects on fertility in both men and women. However, unlike tobacco, cannabis lingers in the body for a longer period, making its negative impact more pronounced.

Summary and recommendations

• Women who smoke should be aware that smoking reduces their fertility.

• Men who smoke should know that tobacco negatively affects sperm quality and that quitting improves reproductive health.

• Couples should understand that secondhand smoke lowers their chances of conceiving.

• Smoking decreases the success rates of assisted reproductive treatments.

• Smoking can have long-term health consequences for future generations.

• Individuals trying to conceive should be offered smoking cessation support to improve their reproductive health.

For those struggling with infertility, quitting smoking should be a top priority. Seeking help to overcome this harmful addiction is a crucial first step toward better reproductive health.

If you need support to quit smoking, visit the website of the Quebec Council on Tobacco and Health for resources and assistance.