How Smoking Affects Fertility, Pregnancy, and Hormones

Most people know that smoking causes cancer and increases the chances of a heart attack. There are graphic ads, warning labels, and conversations about it all around us. But the effects of smoking on reproductive health rarely get talked about. 

Whether you’re trying to conceive or are already pregnant, or just concerned, smoking puts your reproductive health at serious risk. Tobacco use is a common preventable risk factor for many diseases, and fertility is also on the list. Tobacco smoke is a complex mix of more than 4000 chemicals, including nicotine, carbon monoxide, and polycyclic aromatic hydrocarbons, that disrupt hormones, damage reproductive tissue, and can harm developing babies. 

So, can smoking cause infertility? Can smoking cause miscarriage or birth defects? What really happens when you smoke while pregnant? The short answer to all of these is yes. 

This blog breaks down how smoking can impact reproductive health and fertility, what the risks are to the baby, if you’re pregnant, and how tobacco can affect pregnancy at every stage. 

Smoking and hormones

Tobacco smoke enters through your mouth into your lungs. But the effects of it are carried throughout your body. Smoking actively rewires your endocrine system and can affect reproductive hormones. 

The anti-estrogen effect

One of the most significant impacts that smoking has is its suppression of estrogen. Aromatase is an enzyme responsible for converting androgens into estrogen. Nicotine inhibits aromatase, reducing the production of estrogen in the ovaries, adrenal glands, and the central nervous system. This can lead to disrupted follicular and luteal phases, irregular menstrual cycle, and impaired uterine lining development, all of which can affect fertility. 

Increase in androgen 

While estrogen drops, androgen level increases. Research consistently shows that smoking increases the level of androgens in the body, with testosterone levels positively correlating with the number of cigarettes smoked per day. An increase in androgen levels is also associated with failure in quitting, creating a feedback loop that can make it harder to control the problem.

Stress hormone and gonadotropin

People who smoke tend to have higher FSH in the early follicular phase and higher LH levels at menses, both of which are signs of declining ovarian reserve. Smoking also raises cortisol levels, which are proportional to daily cigarette intake, compounding the hormonal imbalance. 

Effect of male hormones

Smoking doesn’t just affect women’s reproductive health. Nicotine interferes with testosterone production at the cellular level. Smokers also tend to have a higher level of SHBG, a protein that binds to testosterone and makes it unavailable for the body to use. Lower free testosterone can affect sperm production and overall sexual health. 

Smoking and female fertility

If you’re someone who is trying to conceive, smoking is working against you at every step. The effects of smoking on fertility are well-documented and go beyond simply making conception harder. Let’s break it down:

Shortage in ovarian reserve

The ovarian reserve is the number and quality of eggs available in the ovaries. Research shows that women who smoke have a significant reduction in the ovarian reserve, up to 20%, and also a reduction in the AMH hormone, indicating a direct impact on ovarian depletion. Tobacco smoke contains polycyclic aromatic hydrocarbons that are toxic to oocytes. This destroys the eggs, which can never be replaced. The long-term consequence of this is that women who smoke enter menopause much sooner than women who don’t. 

Irregular cycle

The hormonal imbalance caused by cigarette smoking, including elevated androgens and lower estrogen, interferes with the ovulation cycle. It can reduce the conception window for each month. Irregular and painful periods are also common in smokers.

Damage to the fallopian tube

Smoking can damage tiny hair-like cilia inside the fallopian tube, which guides the egg from the ovaries to the uterus. Smokers have been found to have more ectopic pregnancies, a dangerous condition where the fertilised egg implants outside the uterus. This can be fatal to the pregnancy and can also be life-threatening to the mother. 

Hostile uterine environment

Even if fertilisation occurs, smoking can create an unhealthy environment in the uterus. Nicotine and cotinine have been detected directly in the follicular fluid and cervical mucus, which is a sign that the ovarian eggs are also exposed to toxins. Among women undergoing IVF, smoking is associated with 45% reduction in the chances of pregnancy, higher miscarriage rates, and 45% reduction in the chances of a live birth. 

Smoking raises the risk of an infertility diagnosis by 85% and doubles the risk of ectopic pregnancy compared to non-smokers. Even secondhand smoke exposure is linked to reduced fertility, meaning the risks extend beyond the person holding the cigarette.

Smoking and male fertility

The conversation around fertility in general often focuses on women, but men’s reproductive health also experiences severe consequences of smoking. 

Sperm quality

Toxic chemicals in tobacco, like nicotine and carbon monoxide, directly damage testicular cells and affect sperm motility, morphology, and count. There are many extensive studies that show that the damage is significant. Research shows that smokers show higher rates of abnormal sperm morphology and lower sperm count compared to non-smokers. 

Smoking doesn’t just affect the volume and movement of sperm; it also attacks it on a genetic level. Smokers show higher DNA fragmentation in sperm, which can increase the risk of transmitting mutations to offspring. Damaged sperm DNA is linked to higher miscarriage rates and developmental problems in children. 

Erectile dysfunction

Smoking affects the ability to conceive naturally. Smokers have a higher risk of erectile dysfunction because smoking narrows the blood vessels, restricting the blood flow needed for an erection. This damage can be directly proportional to the amount smoked and the duration of smoking. 

Risk of prostate cancer

Research has found a clear relationship between smoking and increased overall and cancer-specific mortality in men diagnosed with prostate cancer. This means that smokers don’t just face a higher cancer risk, but also face worse outcomes if diagnosed. 

Smoking during pregnancy

There is no safe amount of smoking during pregnancy. Smoking puts both the mother and the baby at risk, regardless of whether you smoke occasionally or heavily. 

Oxygen deprivation

Every cigarette smoked during pregnancy reduces the amount of oxygen that reaches the baby. Carbon monoxide reduces the blood’s oxygen-carrying capacity, and nicotine raises stress hormones, both constricting blood flow through the placenta. Smoking increases the risk of abnormal bleeding through complications like placenta previa and placental abruption. 

Low birth weight and stunted growth 

Smoking affects the growth of the baby during pregnancy, which can significantly increase the chances of the baby being too small even after the full pregnancy term. This can impact the development of the lungs and brain, and its effects can persist through childhood and into teenage years. Studies link prenatal tobacco exposure to cognitive delays and behavioral problems in children.

Preterm birth

Smoking while pregnant increases the likelihood of premature delivery, and babies born too early can face serious complications, including breathing problems, feeding difficulties, cerebral palsy, developmental delays, and problems with hearing or eyesight. The earlier the birth, the greater the risk.

Can smoking cause birth defects?

Yes. Smoking raises the risk of structural birth defects, including cleft lip and cleft palate, both of which require surgery. Smoking while pregnant also significantly increases the risk of miscarriage and stillbirth.

SIDS 

Babies born to mothers who smoked during pregnancy and those exposed to cigarette smoke after birth have a higher risk of sudden infant death syndrome (SIDS). 

No safe alternatives

Switching to e-cigarettes isn’t a safe workaround: nearly all nicotine products cross the placenta and interfere with fetal development. No tobacco or nicotine product is considered safe during pregnancy.

You don’t have to be a smoker to be harmed by tobacco. For pregnant individuals or people who are trying to conceive, secondhand smoke can have the same damage as smoking directly. 

Can quitting reverse the damage?

The short answer is yes. While some damage, like impact on the ovarian reserve, cannot be undone, many other harms can be reversed. 

The recovery begins quickly. Within just one day of quitting during pregnancy, the baby receives more oxygen, and growth starts to improve. Women who quit smoking before conception or within the first three months of pregnancy reduce the risk of preterm birth to the same level as non-smokers, and those who stop early enough have babies with birth weights similar to those born to non-smokers.

Men tend to recover faster, since sperm take about three months to mature. Men who quit at least three months before trying to conceive can significantly improve their sperm health and fertilization chances.

Hormonally, estrogen and testosterone levels gradually rebalance after cessation, improving the underlying conditions that made conception harder in the first place. 

Quitting Smoking

The good news is that effective, evidence-based tools exist to help you quit, and the reproductive benefits of stopping are real and well-documented.

Varenicline, bupropion, and nicotine replacement therapy (NRT) are all considered first-line therapies for smoking cessation before conception, with each approach roughly twice as effective as placebo. 

For those already pregnant, NRT used alongside counseling has been shown to increase cessation rates in late pregnancy by approximately 40%, with no evidence of negative impact on birth outcomes. 

Behavioral support and counseling remain important complements to any pharmacological approach. 

Smoking systematically undermines reproductive health at every stage, disrupting hormones, damaging eggs and sperm, complicating pregnancy, and endangering newborns. But the body has a remarkable capacity to heal. Whether you’re planning to conceive or already pregnant, quitting is one of the most powerful steps you can take for yourself and for your baby.