The link between smoking and miscarriage is something every pregnant person deserves to understand. Research shows that smoking during pregnancy raises the risk of losing a pregnancy — and the effects can be felt at every stage. This article explains what the science says, which other risk factors matter, and what you can do to protect your pregnancy.
Does Smoking Cause Miscarriage?
Many factors can lead to a miscarriage. In most cases, doctors cannot point to a single cause. However, research consistently shows that smoking and miscarriage are connected.
The most common cause of miscarriage in the first trimester is chromosomal abnormalities. Smoking is one of several risk factors that can raise your chances of pregnancy loss. Other factors include older maternal age, a history of previous miscarriages, and poor nutrition.
It is important to understand that having a risk factor does not mean a miscarriage will happen. It simply means the risk is higher than average.
What Does the Research Say About Smoking and Miscarriage?
Scientists agree that smoking raises the risk of miscarriage, but the exact level of risk is still being studied. When a person smokes, the chemicals in tobacco cross the placenta. This exposes the developing baby directly to harmful substances.
Smoking affects pregnancy in several important ways:
It disrupts how the placenta develops
It damages fetal tissue
It reduces the amount of oxygen the baby receives
A 2022 study reviewed by Healthline raised an important concern. Researchers suggested that some earlier studies may have recorded intentional pregnancy terminations as miscarriages among people who smoked. This could have overstated the link between smoking and pregnancy loss. Even so, the overall body of research still supports a clear connection.
How Smoking Damages the Placenta
The placenta is your baby’s lifeline. It delivers oxygen and nutrients while removing waste. Exposure to cigarette smoke at any stage of pregnancy can damage placental tissue. As a result, this raises the risk of miscarriage and other serious complications.
The damage is not limited to heavy smokers. Even light or occasional smoking can affect how the placenta functions. Therefore, there is no known safe level of smoking during pregnancy.
Miscarriage Risk by Trimester
The risk of miscarriage is not the same throughout pregnancy. Understanding how risk changes by trimester can help you make informed decisions.
First Trimester
The risk of miscarriage is highest in the first three months of pregnancy. Approximately 80% of all pregnancy losses happen during this period. Smoking raises this risk further, because the chemicals in cigarette smoke reach the baby directly during this critical stage of development.
Second Trimester
The overall rate of miscarriage drops significantly in the second trimester. However, pregnancy loss can still occur up to week 20. After week 20, the loss of a pregnancy is no longer called a miscarriage — it is considered a stillbirth.
A 2021 study compared stillbirth rates among pregnant people who smoked, drank alcohol, or did neither after the first trimester. The results were striking:
Non-smokers and non-drinkers: 0.4% stillbirth rate
Those who smoked only: 0.8% stillbirth rate
Those who smoked and drank alcohol: 1.5% stillbirth rate
These numbers show that smoking alone roughly doubles the risk of stillbirth compared to not smoking.
Third Trimester
Miscarriage does not occur in the third trimester. However, smoking still causes serious harm in the final months of pregnancy. It increases the risk of premature birth — when a baby is born before 37 weeks. Furthermore, babies born to people who smoked during pregnancy are more likely to have a low birth weight.
According to researchers, 1 in 5 babies born to mothers who smoked during pregnancy have a low birth weight. Smoking during pregnancy is also linked to:
Birth defects
Newborn health problems
A higher risk of sudden infant death syndrome (SIDS)
The Risk of Second-Hand Smoke During Pregnancy
Second-hand smoke — also called passive smoking — means breathing in smoke from someone else’s cigarette. For pregnant people, this exposure also raises the risk of miscarriage. The toxic chemicals still enter the lungs and can be passed to the baby through the bloodstream.
However, the risk from second-hand smoke is lower than the risk from smoking directly. This does not mean it is safe. The World Health Organization confirms that there is no safe level of tobacco smoke exposure.
Does a Partner’s Smoking Matter?
Yes — and this is an important point that is often overlooked. A 2021 research review found a link between a father’s smoking and a higher risk of miscarriage. The research suggests that paternal smoking before conception — independent of whether the mother smokes — may damage sperm DNA. This damage could affect how the pregnancy develops.
In other words, both partners stopping smoking before and during pregnancy is the safest approach for the baby.
Other Risk Factors for Miscarriage
Smoking is just one of many risk factors for miscarriage. It is helpful to understand the full picture. Other known risk factors include:
Advanced maternal age
High blood pressure
Malnutrition or being significantly underweight or overweight
Physical injuries or trauma
Alcohol consumption
High caffeine intake
Certain physical or genetic health conditions
Having one or more of these risk factors does not guarantee a miscarriage will occur. However, reducing controllable risk factors — like smoking — can make a real difference to your pregnancy outcome.
Quitting Smoking During Pregnancy
Quitting smoking during pregnancy is one of the most powerful steps you can take for your baby’s health. It is also one of the hardest. Nicotine is highly addictive, and many people need support to quit successfully.
The good news is that help is available across Canada. Health Canada offers free resources to help Canadians quit smoking, including online tools, quit lines, and information about nicotine replacement therapy. Your provincial health plan may also cover certain cessation programmes — it is worth checking with your provider.
Talking to your doctor about quitting is a great first step. They can recommend options that are safe to use during pregnancy, such as specific counselling programmes or approved nicotine replacement products. The sooner you quit, the greater the benefit to your baby.
When to See a Doctor
If you are pregnant and currently smoking, speak with your family doctor or midwife as soon as possible. They can help you access quit-smoking support that is safe for pregnancy. You do not need a referral — you can also visit a walk-in clinic if you do not yet have a family doctor.
Contact your doctor right away if you experience any of the following during pregnancy:
Vaginal bleeding or spotting
Cramping or pelvic pain
A sudden decrease in pregnancy symptoms
Fluid or tissue passing from the vagina
These symptoms do not always mean a miscarriage is happening, but they should always be evaluated promptly. Early care gives you and your baby the best possible chance.
Frequently Asked Questions
Can smoking cause a miscarriage?
Research shows a clear link between smoking and miscarriage. When you smoke during pregnancy, harmful chemicals cross the placenta and can damage fetal tissue, disrupt placental development, and reduce oxygen supply to the baby. While smoking may not be the sole cause, it is a well-established risk factor for pregnancy loss.
How much does smoking increase the risk of miscarriage?
The exact increase in risk varies across studies, but the link between smoking and miscarriage is consistent in the research. Some studies suggest that smokers face a significantly higher chance of pregnancy loss compared to non-smokers. There is no known safe amount of smoking during pregnancy.
Is second-hand smoke dangerous during pregnancy?
Yes, second-hand smoke during pregnancy raises the risk of miscarriage and other complications. Toxic chemicals from someone else’s cigarette can still enter your lungs and reach your baby through the bloodstream. The World Health Organization states there is no safe level of tobacco smoke exposure.
Can quitting smoking during pregnancy reduce the risk of miscarriage?
Quitting smoking during pregnancy can reduce the risk of miscarriage and improve outcomes for your baby. The earlier in pregnancy you quit, the greater the benefit. Talk to your family doctor or visit a walk-in clinic to get safe, effective support for quitting.
Does a partner’s smoking affect pregnancy?
Yes. Research suggests that a father’s smoking — even before conception — may damage sperm DNA and affect how the pregnancy develops. Second-hand smoke exposure at home also raises risk for the pregnant person. Both partners quitting smoking is the best approach for a healthy pregnancy.
When during pregnancy is the risk of miscarriage highest?
The risk of miscarriage is highest in the first trimester, with about 80% of all pregnancy losses occurring in the first three months. Smoking and miscarriage risk are closely linked during this period, as cigarette chemicals can directly affect early fetal development. Risk drops in the second trimester but does not disappear entirely.
Key Takeaways
Smoking and miscarriage are linked. Research consistently shows that smoking during pregnancy raises the risk of pregnancy loss.
Chemicals in tobacco cross the placenta. They can damage fetal tissue, disrupt placental development, and reduce oxygen to the baby.
Risk is highest in the first trimester, but smoking causes harm at every stage of pregnancy.
Second-hand smoke also raises risk. There is no safe level of tobacco smoke exposure during pregnancy.
A partner’s smoking matters too. Paternal smoking before and during pregnancy can affect the baby’s development.
Quitting smoking helps. It is never too late to stop — and support is available through your family doctor, walk-in clinic, or Health Canada’s free quit-smoking resources.
Always talk to your doctor. If you are pregnant and smoking, speak with a healthcare provider as soon as possible for guidance that is right for your situation.
This article is for informational purposes only and is not a substitute for professional medical advice. Always consult your family doctor, midwife, or a qualified healthcare provider for guidance specific to your health and pregnancy.
