Smoking during pregnancy: risks for the child
As every mother or soon-to-be mother knows, smoking when pregnant is very harmful to the unborn child. Here is a quick summary of what we know about the harmful effects and how to avoid them.
When is the right time to quit?
Observation of tobacco use in Switzerland reveals that the number of pregnant women who smoke is not negligible! Between 2001 and 2005, 13% of pregnant women admitted that they smoked, as well as 22% of mothers of young children between 0 and 3 years old. However, many female smokers take their pregnancy as an opportunity to quit or to reduce the number of cigarettes they smoke:
- 25% of pregnant women referred to themselves as ex-smokers, as well as 19% of mothers of very young children.
- 90% of female smokers reported having reduced the amount the smoke since the start of their pregnancy and even during the first few years after giving birth.
- 60% of female ex-smokers claimed to have stopped smoking because of their pregnancy, in order to protect their child.
Making the decision to quit is excellent! For one thing, by taking care of her own health, the future mother ensures that she can take care of her child as well as possible in the years to come. In addition, and more importantly, by quitting smoking the woman eliminates one of the main causes of complications during pregnancy.
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Planning a pregnancy
The toxic substances contained in tobacco can cause damage to DNA and human cells. Smoking cigarettes also leads to decreased fertility by interfering with sperm production in men and reducing the number of eggs in a woman’s ovaries. Some epidemiological studies have shown that smoking delays conception by on average two months, and that this effect is directly related to the number of cigarettes that people smoke (Zenzes, 2000). One meta-analysis of the studies even revealed that smoking increased infertility in women by 60% (Augood et al., 1998).
Fortunately, this harmful effect on fertility appears reversible – in time, ex-smokers regain the same level of fertility as those who have never smoked (Augood et al., 1998). Quitting smoking considerably increases fertility.
Dangers to the fetus
Many complications may occur during pregnancy if the mother-to-be smokes. They are principally caused by the carcinogenic and mutagenic toxic substances contained in tobacco (heavy metals, nitrosamines, etc.). Furthermore, Carbon Monoxide (CO), a toxic gas produced by combustion and also found in the pollution present in cities, is absorbed into the woman’s body where it attaches itself to the red blood cells in the place of Oxygen and thus produces an Oxygen deficit (hypoxia). It is worth noting that CO concentration of the blood in the fetus will be 2 to 2.4 times higher than that in the mother.
Tobacco is therefore extremely harmful for a pregnant woman’s unborn child. The birth weight of babies whose mothers smoke is lower than that of babies whose mothers do not smoke. A birth weight which is too low poses a significant risk to the newborn. Women who stop smoking before or during the first trimester of their pregnancy can reduce their risk of giving birth to an underweight baby to the same as that of a non-smoker.
Furthermore, smoking during pregnancy is responsible for the following problems, and the more a person smokes, the more likely these problems are:
- Ectopic pregnancy
- Vaginal bleeding
- Incorrect placement of the placenta or placental abruption
- Premature ruptured membranes and premature birth
- Fetal growth deficiency with a lower average birth weight of the baby (babies born to smokers weigh on average 20 g less than babies born to non-smokers)
- Increased complications in labor for the baby and the mother
- Increased risk of Sudden Infant Death Syndrome (threefold increase)
- Reduced production of breast milk and the transmission of nicotine through breast milk
The overall rate of malformation in babies whose mothers smoke while pregnant does not seem to differ from that of the general population
On the other hand, certain specific malformations are significantly more frequent in babies whose mothers smoke while pregnant, such as cleft lip and palate, gastroschisis (defect in the anterior abdominal wall) and craniosynostoses (skull malformation) in particular.
After birth, the risks continue
The consequences of smoking during pregnancy continue even after a normal birth.
- Nicotine enters the placenta and is transmitted through breast milk, meaning that it acts on the nervous system of the fetus and the breastfeeding baby
- Children whose parents smoke are twice as likely to become smokers themselves as children whose parents do not smoke.
- Children of smokers have more respiratory problems (e.g. asthma and respiratory infections) than the children of non-smokers.
- The risk of cot death is higher among breast-feeding babies whose parents smoke.
- Of course, by quitting smoking, you add several years to your life expectancy and increase your chances of seeing your grandchildren grow up.
Some of these complications may occur even if you have succeeded in not smoking during pregnancy and the first few months after giving birth. Passive smoking can always aggravate asthma and allergies and you will always be a role model for your child, who is more likely to start smoking as a teenager if you smoked when they were growing up.
Quitting during pregnancy: what help is available?
The best time to start smoking is before pregnancy, both to increase the chances of conception and to protect the health of the unborn child. At this point, every type of cessation aid is available to you. You can take a look at the Tips and Medication sections to find some tried and tested methods. Asking for support is also a very effective method! Talk about it with your friends and family, or call in at a consultation centre near you. On the forum you will find professionals and other web users who are there to guide and support you.
If you are already pregnant, you also have access to the vast majority of smoking cessation aids. Although nicotine replacement therapy during pregnancy is controversial, it can sometimes be used. Nicotine is well and truly harmful to the fetus, but if the substitution compensates for a large number of cigarettes, the benefits can be immense, especially to the oxygen levels of the fetus. Indeed, a substitute will always be less harmful than a cigarette because it supplies just nicotine and not the thousands of other toxic substances such as carbon monoxide, a dangerous gas given off by the burning of cigarettes. In any case, the expected benefits must carefully be weighed against the potential risks by you and your doctor, obstetrician, or tobacco addiction specialist.
All the other methods – such as cognitive-behavioral therapy, books and self-help brochures, appointments or help on the Internet – remain available.
- M.-P. Cournot, F. Assari-Merabtene, C. Vauzelle-Gardier, E. Eléfant, Centre de Renseignements sur les Agents Tératogènes, Hôpital Armand-Trousseau, 26, avenue du Docteur-Netter, 75012 Paris.
- The effect of maternal smoking on respiratory and arousal patterns in preterm infants during sleep. Hemant Sawnani, Tonya Jackson, Thomas Murphy, Robert Beckerman and Narong Simakajornboon
- Augood C, Duckitt K, Templeton AA. (1998). Smoking and female infertility: a systematic review and meta-analysis.
- Keller R., Radtke T., Füllemann D., Krebs H., Hornung R. (2009). Tabagisme et grossesse: monitorage sur le tabac - Enquête suisse sur le tabagisme. Enquête mandatée par l'Office fédéral de la santé publique (OFSP), financé par le Fonds de prévention du tabagisme.
- Murin S., Rafii R., Bilello K. (2011). Smocking and smocking cessation in pregnancy. Clinics in Chest Medicine, 32(1), 75-91.
- Zenzes MT. (2000). Smoking and reproduction: gene damage to human gametes and embryos. Hum Reprod
To find out more
“Pregnancy and Smoking” Questions & Answers
(Answers from Dr. Jean-Paul Humair, specialized tobacco addiction doctor at the University Hospital of Geneva)
Question: I’m pregnant, but I don’t really want to quit cigarettes, as I enjoy smoking. Is it really so bad to smoke while pregnant?
Answer: Smoking puts your unborn child at very serious risk. You are advised to stop smoking as soon as possible (see our brochure for women on the website).
Question: I’m one month pregnant and would like to quit smoking. Given that with my first child I was not able to stop either during pregnancy or during breastfeeding, what anti-smoking aids are available to me (patches, Zyban, etc.)?
- Zyban and pregnancy: as with many medicines, there is only a small amount of data on the effects of Zyban during pregnancy in women. Zyban produces no known toxic effects on the development of the fetus during pregnancy, and no known malformation. Although its use is preferred outside pregnancy, it is possible all the same to take it during pregnancy. Speak to your doctor or gynecologist in order to discuss the best course of action – you should bear in mind the risks of inhaling tobacco during pregnancy, which are well documented given that smoking increases the risks of miscarriage and premature birth. If you are planning a pregnancy, you should allow about 1 week for Zyban to be eliminated from your system after you stop taking it. Given that the active ingredient in Zyban is transmitted through breast milk, breastfeeding is not advised while Zyban is being taken.
- Nicotine replacements and pregnancy: nicotine replacements may be used by women who are not able to stop smoking without the help of medication. Short-acting replacements are preferred (this applies to all replacements, e.g. choose the shortest-acting patches). Nicotine has not been shown to be harmful to the fetus, and replacements only provide 50-60% of the nicotine absorbed while smoking. Tobacco, on the other hand, is clearly toxic for the fetus, not because of the nicotine but because of the more than 4,000 other substances that it contains, and the Carbon Monoxide that is released by burning a cigarette.