Smoking during pregnancy is arguably the worst thing a woman can do for the health of the unborn baby. For some women, being pregnant is the perfect argument to quit smoking completely, even after childbirth. However, for others, the addiction is still too strong.

Despite public health campaigns, tobacco use continues to be common among women. It is estimated that 12% of American women still smoke cigarettes today. According to the Centers for Disease Control and Prevention, 7.2% of women who gave birth in 2016 smoked cigarettes during their pregnancy. Most of them think that reducing their tobacco consumption might be enough not to endanger the life of the fetus, but this is not the case since even one cigarette per day can cause harmful effects.

The toxicity of tobacco

The composition of tobacco smoke is complex. It depends on the type of tobacco, the additives and the method of consumption. Over 4000 substances have been identified.

  • 10 to 15% carbon dioxide.
  • 3 to 6% carbon monoxide.
  • 0.1 to 0.2% hydrocyanic acid,
  • Volatile organic compounds (1 to 3%) such as aldehydes, ketones and hydrocarbons.
  • Carcinogenic substances (polyaromatic hydrocarbons, nitro derivatives, aldehydes, nitrosamines, ketones, benzene, radioactive elements).
  • Irritants (acrolein).
  • Metals (nickel, cadmium).
  • Free radicals (quinones, hydroquinone, epoxides, CO, peroxide compounds).
  • Nicotine.

The main constituents of tobacco have the capacity to cross the placental barrier and reach the fetus. The maternal level of carboxyhemoglobin varies from 5 to 15% for a consumption of 20 cigarettes per day and that of the fetus is equal to 1.8 times that of the mother.

The consumption of tobacco can be assessed precisely by the dosage of cotinine. Cotinine represents 80% of the breakdown products of nicotine. It is present in all biological media (blood, urine, saliva, milk, hair, amniotic fluid, etc.). Cotinine is found in the fetus and in the amniotic fluid (30 to 45% of the levels of smoking mothers).

The risks of smoking for baby

  • An increased risk of infertility

The toxic substances contained in tobacco damage DNA and human cells: smoking cigarettes thus leads to a decrease in fertility by disrupting sperm production in men and by reducing the number of oocytes per ovary in women.

Some epidemiological studies have shown that smoking delays conception by an average of two months and that this effect is directly related to the number of cigarettes people smoke. A meta-analysis of studies even found that smoking increased the risk of infertility in women by 60%.

Fortunately, this detrimental effect on fertility appears to be reversible: over time ex-smokers recover the same fertility rates of those who have never smoked.

The success rate of in vitro fertilization is also reduced. Stopping smoking greatly increases fertility and fertility.

  • Weight problems

A studies has shown that the impact of smoking on the weight of the baby at birth and the result is final.

Carried out on 371 pregnant women, all smokers, the study led by a team of French researchers established four categories: 192 women who smoked less than five cigarettes a day, 122 between five and nine, 37 ten or more and 20 of them had completely quit smoking.

The aim of this study was to see the variations in weight on different babies, according to their mother’s tobacco consumption.

The researchers therefore took into account other factors that could impact the weight of babies (the sex of the baby, the weight of the mother before pregnancy). The results are astounding since compared to the weights of babies whose mothers had quit smoking, the babies lost about 228 grams if the mother smoked less than five cigarettes per day, 251 grams if the mother smoked between five and nine per day and 262 grams if she smoked ten or more.

The researchers who conducted this survey therefore wish to alarm future mothers of the risks of tobacco on their child. This is because a baby who is born lighter than average has a higher risk of developing health problems afterwards.

  • Ectopic pregnancy

The risk of ectopic pregnancy is increased in women smokers (the greater the consumption, the greater the risk). Nicotine decreases tubal mobility (the ability to move inside the tubes) with spasms and reduced beating of the cilia responsible for pushing the embryo into the uterus, thus increasing the risk of ectopic pregnancy.

This risk returns to that of the general population if tobacco consumption is stopped 1 month before conception.

  • Premature birth

The risk of premature birth is increased in women who smoke, especially due to premature rupture of membranes.

The premature rupture of membranes before a term of 34 weeks is three times more frequent in women smokers. This risk is also related to the age of the mother.

It is important to note that this increased risk disappears if the woman stops smoking before conception and decreases markedly if the cessation of smoking intoxication occurs in the first trimester of pregnancy.

  • Miscarriage

The risk of spontaneous miscarriage is also increased. In female smokers, it is multiplied by 1.5 to 3. In heavy smokers (more than 20 cigarettes per day) the risk of spontaneous miscarriage is 20% against 10% in non-smokers.

It can reach 35% if the consumption is 35 cigarettes per day. The risk of miscarriage is also increased in passive smoking (at least one hour per day).

This is due to a poor quality of the endometrium which becomes unsuitable for implantation as well as an alteration of the oocytes, a decrease in uterine blood flow and an alteration of the blastocyte (stage of the embryo between the fifth and the seventh day after fertilization) by nicotine.

Other consequences of smoking during pregnancy

Tobacco also increases the frequency of a large number of pathologies in pregnancy:

  • The risk of metrorrhagia,
  • The relative risk of retroplacental hematoma is multiplied by 1.5,
  • The risk of low insertion of the placenta is multiplied by 2 to 3. The placenta in smokers has a larger surface area due to hypoxia,
  • High blood pressure during pregnancy is less common in women who smoke, but it is more serious when it occurs.
  • Decrease in immune defenses (especially in cases of infection): an American study has shown that genetic mutations are induced in utero by smoking. Mothers exposed to their partner’s cigarette smoke during pregnancy give birth to newborns presenting more frequently than others a genetic “failure” of their immune cells,
  • The increase in oral pathologies,
  • The increased risk of stretch marks,
  • The increase in healing abnormalities after cesarean section, changes in certain laboratory parameters (blood sugar, insulin level, HGC).

The effects of tobacco on the fetus

The first risk in the fetus is that of increased Intrauterine growth restriction (IUGR). The relationship between the amount of tobacco consumed per day and the birth weight deficit is not linear.

Even low tobacco consumption affects fetal growth. The prevalence of IUGR goes from 8.5% to 14.7% for consumption of 1 to 5 cigarettes per day and to 18.7% if it exceeds 10 cigarettes per day.

Maternal smoking could also cause fetal malformations. This point is controversial, however. Some studies have suggested a possible increase in neural tube defects, cleft lip and palate, limb abnormalities, urinary or cardiac malformations. This risk seems significant for consumption of more than 20 cigarettes per day.

Another risk associated with tobacco during pregnancy: fetal death in utero. 11% of late fetal deaths are thought to be attributable to tobacco because of placental complications and the risk of intrauterine growth.

Finally, tobacco decreases the frequency of the fetal respiratory rate, the variability of the fetal heart rate, fetal movements and it increases the cardiac output and the heart rate.

The Effects of Tobacco on Newborns and Infants

There is no increased risk of neonatal death in children born after exposure to tobacco during pregnancy, but there is an increased risk of sudden infant death syndrome. This risk, apparently dose dependent, would be multiplied by 2 if the mother smoked during pregnancy.

In addition, the frequency and duration of obstructive sleep apnea are higher in children of smoking mothers. The duration of apnea is linked to the number of cigarettes smoked by the mother.

The effects of smoking during breastfeeding

If you are breastfeeding and smoking, keep in mind that the pollutants of a cigarette accumulate in breast milk. In addition to nicotine, dioxins, benzopyrenes, nitrosamines and heavy metals enter the milk from the smoke of the cigarette and into the infant’s gastrointestinal tract.

Smoking also lowers prolactin levels, especially at the beginning of breastfeeding. Tobacco decreases milk production by lowering prolactin levels (30 to 50%). The more you smoke, the more severe the impairments. In addition, nicotine changes the taste of milk, so the baby may end up not liking it.

The effects of smoking during breastfeeding on the child’s health in the long term is difficult to quantify. However, direct observations show that babies of smoking mothers drink less, are more restless, vomit more often and suffer from colic and grow more slowly. Children from smoking households are also at a higher risk of respiratory diseases, middle ear infections, lung problems and sudden infant death.

The risk of allergies also seems to be increased. These complications are due not only to the pollutant-contaminated breast milk, but also to the passive smoke, from which every baby must be actively protected. Not only the mother but also the father is therefore responsible and should leave the house for smoking.

The risks of maternal smoking on the child

Maternal smoking also promotes the development of respiratory infections and asthma. The incidence of wheezing episodes is thus estimated to be 45% during the first year in children of smoking mothers.

Finally, tobacco increases the systolic blood pressure of the newborn (for 6 months to 1 year)

Some researches have found a relationship between tobacco consumption during pregnancy and the psychomotor or cognitive development of the child. Thus, a study of 17,000 children demonstrated a significant decrease in reading and mathematics scores at the ages of 7, 11 and 16, and a low socio-professional level at the age of 23 in the group of subjects exposed to tobacco during pregnancy.

The follow-up of 1,265 children over 15 also showed a significant increase in behavioral disturbances in those whose mothers smoked more than 20 cigarettes per day during pregnancy.

However, it is difficult to assess the specific risk associated with the exposure of the fetus to tobacco on the brain development of the child; indeed, other factors that can affect this development often coexist with maternal smoking.

Children of a smoker are twice as likely to become smokers themselves as children of non-smokers.

How to stop smoking during pregnancy

Because of all the risks of smoking on the development of the fetus and the future of the child, an expectant mother should stop smoking at all cost.

This cessation should ideally be total. To facilitate the transition the mother can undergo nicotine replacement therapy. The use of these nicotine substitutes, however, must be done under medical supervision for pregnant or breastfeeding women.

If you did not quit smoking before your pregnancy, get help to quit as soon as possible. Whatever the moment, stopping is always beneficial. If your partner smokes, encourage him or her to quit: passive smoking has the same risk factors as active smoking. Hence the reason why specialists do not recommend expectant mothers to just reduce their tobacco consumption, but to simply quit smoking permanently during pregnancy and even at the time of conception.

Tobacco can be a real scourge during pregnancy. Of course, by quitting smoking you not only protect the health of the baby, but you also add several years to your own life expectancy and increase your chances of seeing your grandchildren grow up.

Cassidy Perry

A certified dietician specializing in diabetes care, Cassidy has over a decade of experience working with diverse patient backgrounds. She writes health-related articles for the Scientific Origin.