Smoking in Pregnancy: Risks, Effects and How to Quit

Are you a smoker? Then you've almost certainly tried – or at least thought about – giving up. And you'll know just as well that it's anything but easy. But what do you do when a pregnancy suddenly enters the picture? Every cigarette contains over 4,000 substances, many of them toxic – which raises the likelihood that smoking during pregnancy will harm your baby.

And so the search for alternatives begins. But what if you only smoke occasionally, just the one cigarette? What if you swap smoking for vaping? The truth – however much we might like to soften it – is unambiguous: there is no safe level of smoking in pregnancy. Stopping, on the other hand, brings genuine benefits at any point, both for you and your baby. That's exactly what we'll focus on in this article.

We'll look at the effects of smoking on mother and foetus, why it's so dangerous and – most importantly – how to stop, plus what you can do if you've already smoked during your pregnancy.

In brief:

• There is no safe number of cigarettes in pregnancy – even occasional smoking can be dangerous.
• Smoking increases the risk of premature birth, low birth weight, placental complications and birth defects.
• Stopping is worthwhile at any point, especially before 15 weeks of pregnancy – but it's never too late.
• E-cigarettes and shisha are not safer alternatives; passive smoking can harm your baby too.
• You can turn to your GP, obstetrician or a stop-smoking service for support in giving up.

Why smoking in pregnancy is dangerous

Let's start by clarifying what smoking in pregnancy actually does. Where does this great danger to mother and foetus come from?

Studies show that a single cigarette contains over 4,000 chemical substances, which pass rapidly from the mother's blood to the foetus via the placenta. Many of these can have harmful effects, but the two main culprits are nicotine and carbon monoxide:

• Nicotine narrows the blood vessels during pregnancy, reducing the supply of oxygen and nutrients to the baby.
• Carbon monoxide binds to haemoglobin and takes the place of oxygen – so the foetus receives less oxygen than it needs for normal development.

To picture more clearly what these substances do inside your baby's body, imagine this: every cigarette creates a kind of slow suffocation of the foetus for several minutes. Of course, that doesn't mean it stops breathing altogether – but it gets less oxygen and fewer of the resources it needs to grow normally.

This principle doesn't apply only to smoking: the same thing happens with all nicotine-containing alternatives, such as e-cigarettes or vapes. Although their composition differs from that of a conventional cigarette, the nicotine still reaches the foetus and can affect its development.

Effects and risks of smoking for the foetus

Nicotine and carbon monoxide explain why smoking in pregnancy is dangerous – but not exactly how. So what dangers are you exposing your baby to if you don't give up smoking? Let's talk in more detail about the risks of smoking in pregnancy and what actually happens to the foetus.

As we said: when you smoke, oxygen and nutrients reach your baby in smaller amounts. And a shortage of sufficient oxygen and nutrients can affect how the pregnancy develops from the very first weeks, leading to various consequences for the foetus:

• Ectopic pregnancy or miscarriage: nicotine can interfere with implantation of the embryo and the normal development of the pregnancy, increasing the risk of ectopic pregnancy and miscarriage.
• Growth restriction and low birth weight: the reduced supply of oxygen and nutrients can slow your baby's development, which is why it may be born weighing less than normal.
• Premature birth: smoking increases the likelihood of labour starting before term – the newborn then faces a higher risk of respiratory and neurological complications.
• Congenital abnormalities: smoking is linked to an increased risk of birth defects, particularly cleft lip and palate.
• Placental complications: nicotine can impair placental function and increase the risk of placental abruption or placenta praevia.
• Stillbirth: persistently reduced oxygen supply and placental complications can increase the risk of intrauterine death.

If you decide to stop smoking completely – even once the pregnancy has already begun – you can significantly reduce many of these consequences.

Long-term effects on the child

The consequences of smoking in pregnancy don't vanish as if by magic at birth. Exposure to nicotine and carbon monoxide during life in the womb can affect a child's health from the first days after birth right through the early years and beyond. So it isn't just a matter of immediate dangers to the pregnancy, but also of long-term risks in the child's life.

Babies exposed during pregnancy have a higher risk of sudden infant death syndrome (SIDS), as well as respiratory problems such as wheezing and childhood asthma. Respiratory infections such as bronchiolitis and pneumonia are also more common among them.

Studies also point to a possible link between smoking in pregnancy and an increased risk of obesity or attention and behavioural disorders. However, several factors play a part in these associations, and smoking is considered a risk factor rather than a direct cause.

Effects on the mother and on fertility

We've talked about what smoking can do to your child – now let's look at what it does to you. How does smoking affect the life of a mum-to-be?

First of all, smoking and fertility are closely linked. And not only in women, but in men too. Women who smoke often have poorer egg quality, may have problems with ovulation and carry a higher risk of female infertility. In men, smoking can reduce sperm quality and motility. That's precisely why both partners are advised to stop smoking before conception when trying for a baby, in order to improve the chances of conceiving during the fertile window.

And what happens during pregnancy? Smoking also increases the risk of complications for the mother. Essentially, nicotine and carbon monoxide act on the placenta and can jeopardise the normal course of the pregnancy.

Smoking by trimester – first month, first trimester, third trimester

There is no point in pregnancy at which smoking can be considered safe. Nor is there a number of cigarettes you could smoke without risk – but you should know that the risk rises with the dose and differs at each stage.

Smoking in the first weeks of pregnancy is dangerous because it coincides with the stage when the foetus's organs are forming – which can lead to birth defects. The final months, on the other hand, are crucial for growth, which is why smoking in the third trimester has the greatest negative impact on the foetus's weight and growth. You'll understand better what happens at each stage if you follow your baby's development by trimester.

In the first month of pregnancy, smoking may simply remain a habit, and it only becomes clear later that it has turned into a danger – namely when you find out you're pregnant. Yet it's precisely at this stage that implantation and the formation of embryonic structures begin, which is why you should stop as soon as the pregnancy is confirmed.

Smoking in the first trimester carries the greatest risk for organ development, particularly in terms of congenital abnormalities. Studies show that if you stop before around 15 weeks, you can successfully reduce many of the risks associated with smoking.

Smoking in the final trimester mainly affects the rate at which the foetus grows. At this stage, the risk of growth restriction, low birth weight and premature birth increases.

What should you take away from all this above all? Stopping smoking helps in every trimester. Yes, the benefits are greater the earlier you stop – but whichever trimester you're in, stopping from now on counts and has a positive effect on your health and your child's.

"I smoked before I knew I was pregnant" – what now?

If you've just found out you're pregnant and your first thought is "I smoked during pregnancy without knowing", don't panic. Of course it isn't ideal, but what matters most is what you do from now on.

Many women only discover they're pregnant after a few weeks. And because they don't know beforehand, they carry on smoking until they get the first confirmation: either through clear early signs or through pregnancy tests.

You can't change the past. There's no point panicking, nor blaming yourself for the period before you knew. The changes that count are the ones you can make from now on.

Stop smoking and tell your doctor that you smoked in the first weeks of pregnancy, so they can give you the right advice. The sooner you stop, the more you reduce the risks – and reap the benefits, even though the pregnancy has already begun.

How many cigarettes are dangerous? Is there a safe level?

The more cigarettes you smoke, the greater the risks to your pregnancy. And here lies a little trap that many smokers fall into: "So does that mean if I smoke less, the risk goes down?" And of course the next question follows immediately: "How many cigarettes am I allowed to smoke in pregnancy?" And so the original goal of stopping altogether to protect your child and yourself suddenly turns into a negotiation over the number of cigarettes permitted.

Unfortunately, the answer isn't that nuanced – and it isn't negotiable either. Smoking exposes the foetus to nicotine and other toxic substances that can harm it – including occasional smoking, including a small number of cigarettes. It's tempting to say: "One cigarette won't do any harm." But reality contradicts that myth. Even a single cigarette exposes the foetus to substances that can reduce its oxygen supply.

Cutting down the number of cigarettes is definitely a step in the right direction if you can't stop straight away – but the goal for a healthy pregnancy is to give up completely. 

Passive smoking in pregnancy

Passive smoking means breathing in other smokers' smoke. Even if you don't smoke yourself, passive smoking in pregnancy can affect your pregnancy and your baby. The toxins you inhale also pass into your blood – regardless of whether they come from your own cigarettes or someone else's. There's even the concept of thirdhand smoke, the smoke residue left behind on clothing, hair, furniture and other surfaces.

All these toxic chemicals cross the placenta and can increase the risk of low birth weight or other health problems. Exposure is also linked to a higher risk of sudden infant death syndrome (SIDS) and of respiratory infections after birth. 

That's why it's important that your partner and other family members don't smoke near you or in the home during your pregnancy. If your partner gives up too, it not only protects your baby but can also help you break the habit more easily.

E-cigarettes, vaping and shisha in pregnancy

Wondering whether there are safer alternatives to smoking? Vaping, for instance? E-cigarettes? Shisha? We know how hard it can be to give up a long-standing habit – so we understand why you're looking for the safest option for your baby.

But the truth is: the safest option in pregnancy is zero nicotine. Whatever the method of consumption, no nicotine product can be considered safe – and here's why:

• E-cigarettes in pregnancy: the vapour can contain nicotine and other substances that reach the foetus.
• Vaping in pregnancy: although the aerosols don't contain tar from burning tobacco, the vapour can still contain nicotine.
• Shisha in pregnancy: the idea that the water filters out the toxins is a myth – the water merely cools the smoke, it doesn't trap the toxins; the smoke you inhale remains dangerous.
• Nicotine pouches and chewing tobacco: these still deliver nicotine, which can affect the foetus's development, even though they eliminate carbon monoxide exposure.

If you smoke and can't manage to stop any other way, switching from cigarettes to vaping can reduce exposure to certain toxins, since there's no combustion and therefore no carbon monoxide. That doesn't mean, however, that vaping in pregnancy is considered safe.

How to stop smoking in pregnancy (methods and support)

We know how hard it can be to give up a habit like smoking. But every day without cigarettes counts for your baby, and the benefits appear far more quickly than you might think. About 24 hours after your last cigarette, the carbon monoxide level in your blood drops and the oxygen available to the foetus already improves.

What's more, you don't need to pile pressure on yourself to stop immediately, alone and without any help. Get professional support and take it step by step.

• For most women, the recommended first step is behavioural counselling with professional support. Your GP, obstetrician or a specialist stop-smoking programme can help you draw up a realistic plan and manage nicotine cravings.
• There are also solutions if counselling alone isn't enough. Your doctor may consider nicotine replacement therapy. This delivers nicotine without carbon monoxide and the other toxins produced by burning tobacco, and can therefore be less harmful than continuing to smoke.

But don't reach straight for medication or stop-smoking products on your own initiative during pregnancy. The right method for you has to be chosen together with your doctor – depending on how much you smoke, what stage of pregnancy you're at and what you've already tried. With patches, your doctor may advise removing them before you go to bed.

Smoking and breastfeeding

We're sure you were expecting this verdict: smoking while breastfeeding is not advisable. Nicotine and other harmful substances can pass into breast milk and cause sleep problems, digestive upsets and other risks for your baby.

The good news is that you don't have to stop breastfeeding just because you haven't given up smoking. Breast milk remains the recommended option because of its many benefits – you simply need to be careful enough to reduce your baby's exposure.

Smoke outdoors only, never in the house or the car, wash your hands thoroughly, tie your hair back and change your clothes before picking your baby up – because passive smoking after birth increases the risk of SIDS and respiratory infections.

Frequently asked questions 

You recognised yourself in this article, but now the question remains: "Okay, so what happens next?" According to CDC data from 2021, more than half of women who smoked before pregnancy managed to stop during pregnancy – so giving up is possible. You can do it too, and you can get the support you need at any time. In the meantime, here are some helpful answers to a few of the most common questions from pregnant women thinking about stopping smoking for their own health and their baby's.

I smoked before I knew I was pregnant. Is that bad?

Having smoked before your pregnancy was confirmed doesn't automatically mean your baby will have a problem – especially if you stopped once you found out. What matters is stopping as quickly as possible and telling your doctor about the exposure in those first weeks.

How many cigarettes a day are dangerous in pregnancy?

There is no number of cigarettes that is considered safe in pregnancy – not even occasional smoking. Even a single cigarette can reduce your baby's oxygen supply and expose it to nicotine and other toxins.

Is cutting down better than stopping altogether?

Reducing the number of cigarettes is a step forward if you can't stop straight away – but it doesn't eliminate the risks of smoking. The ideal for you and your baby is to give up completely, and that decision is beneficial at any point in pregnancy.

Can I use an e-cigarette (vape) in pregnancy?

Neither ordinary cigarettes nor e-cigarettes are considered safe in pregnancy. Although the aerosols don't contain tar from burning tobacco, the vapour can still contain nicotine and other dangerous substances. If you can't manage to give up conventional cigarettes, it's better to talk to your doctor about a stop-smoking method suitable for pregnancy rather than switching to vaping on your own.

Are nicotine patches or nicotine gum safe?

Your doctor may consider nicotine replacement therapy if counselling isn't enough – but only after careful consideration. Don't opt for such solutions on your own without medical advice. The risks and benefits need to be weighed up individually, because nicotine too can affect the foetus.

My husband smokes. Does that harm my baby?

Yes, second-hand smoke during pregnancy increases the risk of low birth weight and premature birth. If your partner won't give up, he should smoke outdoors only and keep the home and car completely smoke-free.

I smoked throughout my pregnancy – is it still worth stopping now?

Yes, absolutely. Stopping can improve your health and reduce the negative effects on your baby's growth at any point in pregnancy – even though the benefits are greater the earlier you stop.

Can I smoke if I'm breastfeeding?

Ideally you wouldn't smoke, because nicotine and other harmful substances can pass into breast milk, and second-hand smoke harms your baby. But if you can't manage to stop, breastfeeding is still recommended. You just need to make sure you smoke outdoors only and change your clothes before picking your baby up, to keep exposure as low as possible.

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