What effects does smoking during pregnancy have on the baby?

By (gynecologist), (embryologist) and (psychologist).
Last Update: 03/28/2022

Smoking during pregnancy is strongly discouraged due to the effects of nicotine on the fetus.

Babies born to mothers who smoke are at an increased risk of showing signs of withdrawal syndrome at birth, such as irritability, tremors, and sleep disturbances.

In the long term, smoking in pregnancy can lead to behavioral deficits in children, lower IQ, inattention, and hyperactivity.

Effects of tobacco

Tobacco contains a multitude of harmful and carcinogenic compounds such as cyanide or lead, but the most dangerous for the developing baby are nicotine and carbon monoxide.

When smoking, all these compounds pass into the blood and will therefore reach the fetus through the umbilical cord in smoker mothers.

Maternal blood is the main source of oxygen and nutrients for the fetus throughout pregnancy.

It is believed that nicotine and carbon monoxide can reduce the amount of oxygen the baby receives and, as a consequence, affect its normal development in the uterus.

Below, we will discuss some of the risks that babies of smoking mothers may suffer.

Low birth weight.

Tobacco use doubles the risk of low birth weight. On average, children born to mothers who smoke weigh an average of 200 grams less. The main reasons for this are as follows:

Insufficient development of the fetus
not enough oxygen reaches the fetus because of two factors. Nicotine acts to narrow the blood vessels and carbon monoxide binds to red blood cells and displaces oxygen.
Premature delivery
due to premature rupture of the sac or placental complications. For example, there is an increased risk of placenta previa, in which the placenta is located low in the womb and covers the cervix, or of placental abruption before delivery.

It is also very likely that both will happen simultaneously. In the most severe cases, when nicotine levels are very high, spontaneous abortion or intrauterine fetal death may occur, resulting in the birth of a stillborn baby.

Risks in the newborn

After birth, babies born to mothers who smoke may present various complications due to their exposure to the toxic substances in tobacco throughout gestation. These are discussed below:

Congenital malformations.
cleft lip, cleft palate, cardiac malformations, etc.
Withdrawal syndrome in newborns
infants may exhibit the same withdrawal symptoms as adults, which manifest as stress, anxiety and irritability.
Respiratory problems
such as infections leading to otitis, bronchitis or pneumonia. There is also an increased risk of asthma and allergies. Sometimes it is necessary to use ventilators to help them when they have a crisis.
Sudden Infant Death Syndrome (SIDS)
consists of the sudden death of an apparently healthy infant under one year of age, without being able to clarify the exact cause of death.

Women who decide to have a child should be aware of the effects of tobacco consumption in order to avoid being exposed and not cause harm to the newborn.

Exposure to tobacco smoke of non-smoking women also influences the likelihood of low birth weight, as well as other complications.

Smoking during lactation

The effects that smoking can have on the baby do not end with delivery. If the mother continues to smoke while breastfeeding, nicotine and other toxic substances can also be transmitted through breast milk.

The symptoms and complications this will cause in the nursing infant are as follows:

  • Colic
  • Difficulty in breastfeeding
  • Palpitations and nervousness
  • Sleeping for shorter periods
  • Shorter duration of breastfeeding
  • Sudden Infant Death Syndrome (SIDS)

For all these reasons, it is advisable for women not to start smoking again after giving birth.

If you have not quit smoking during pregnancy, there are some considerations to take into account when breastfeeding your baby, such as smoking after breastfeeding and not before, smoking outdoors and not indoors, and reducing the number of cigarettes you smoke per day as much as possible.

Long-term complications

Occasionally, babies born to smoking mothers do not present any of the aforementioned alterations at the time of birth. This does not mean that other complications may not appear later in life.

It is common for children exposed to tobacco smoke to present behavioral and learning problems. Other disorders that have been associated with smoking during pregnancy include the following:

  • Attention deficit
  • Hyperactivity
  • Tendency to have high blood pressure
  • Predisposition to caries problems
  • Childhood overweight or obesity

In addition, children of female smokers will be more likely to smoke once they reach adulthood.

Advantages of not smoking

It is best to stop smoking at the time of planning a pregnancy, i.e. before conception, and not when the woman already knows she is pregnant.

However, quitting smoking during pregnancy, whether in the first, second, or third trimester, will bring benefits to the health of the future baby.

Obviously, the sooner you quit smoking, the better. It should be noted that the development of the main organs and systems of the organism takes place during the first weeks of gestation.

Quitting smoking has multiple benefits for both the mother and the fetus. These are discussed below:

  • The fetus receives more oxygen, even 24 hours after quitting smoking.
  • The fetus has a better development and grows at the right pace.
  • Rates of miscarriage or premature delivery decrease considerably.
  • The mother feels more energetic and can breathe more easily.
  • There is increased milk production during lactation.
  • The possible alterations in newborns exposed to tobacco are reduced.

FAQs from users

By Blanca Paraíso M.D., Ph.D., M.Sc. (gynecologist).

The ideal for a woman seeking pregnancy is to quit smoking as soon as possible. The deleterious effect on the eggs will not be recoverable, so that, if assisted reproduction techniques are required, the number and quality of the eggs obtained will most likely be lower than would correspond to a woman of the same age.

However, there are studies that postulate that smoking also has an effect on endometrial receptivity. It is possible, although there is no clear evidence, that this effect can be reversed by quitting smoking, so it would make sense to stop smoking at least one cycle before you start looking for pregnancy.

What is clear is that once pregnant, smoking should be avoided as much as possible, in order to facilitate proper placentation and not expose the baby to risks.
Read more

What are the consequences of smoking in the first month of pregnancy?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

Smoking has negative effects on the fetus in any month of pregnancy. However, smoking during the first weeks of gestation increases the risk of miscarriage and fetal malformations, since it is during this time that all embryonic development takes place with the formation of specific tissues and organs.

Is it true that smoking 5 cigarettes a day during pregnancy is safe?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

No. There is no exact amount of tobacco that is safe for the fetus. It is true that smoking a few cigarettes a day is better than a pack, but it should be noted that smokers' bodies are especially sensitive to the first few doses of nicotine each day. Therefore, the difference between smoking a few cigarettes a day or many is not so great.

Is smoking joints while pregnant bad?

By Zaira Salvador B.Sc., M.Sc. (embryologist).

Yes, smoking hashish or marijuana while pregnant has negative effects on the fetus. As with tobacco, the baby may be born prematurely and with low birth weight, in addition to presenting withdrawal symptoms (crying, tremors, altered sleep pattern, etc.).

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Authors and contributors

 Blanca Paraíso
Blanca Paraíso
M.D., Ph.D., M.Sc.
Bachelor's Degree in Medicine and Ph.D from the Complutense University of Madrid (UCM). Postgraduate Course in Statistics of Health Sciences. Doctor specialized in Obstetrics & Gynecology, and Assisted Procreation. More information about Blanca Paraíso
License: 454505579
 Zaira Salvador
Zaira Salvador
B.Sc., M.Sc.
Bachelor's Degree in Biotechnology from the Technical University of Valencia (UPV). Biotechnology Degree from the National University of Ireland en Galway (NUIG) and embryologist specializing in Assisted Reproduction, with a Master's Degree in Biotechnology of Human Reproduction from the University of Valencia (UV) and the Valencian Infertility Institute (IVI) More information about Zaira Salvador
License: 3185-CV
Adapted into english by:
 Cristina  Algarra Goosman
Cristina Algarra Goosman
B.Sc., M.Sc.
Graduated in Psychology by the University of Valencia (UV) and specialized in Clinical Psychology by the European University Center and specific training in Infertility: Legal, Medical and Psychosocial Aspects by University of Valencia (UV) and ADEIT.
More information about Cristina Algarra Goosman
Member number: CV16874

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