What Happens to My Baby If I Smoke during Pregnancy? Development of Oxygen Sensitivity in Infants of Smoking and Non-smoking Mothers.

5 mins read

The negative effects of maternal cigarette consumption have been studied for a long time. Smoking during pregnancy mainly damages the infant’s cardiovascular function and overall growth. In both scenarios, the repercussions are severe and irreversible. However, its impact on a baby’s respiratory system has not been studied exhaustively.

The reasons for the lack of studies are simple. Many women smokers give up cigarettes during pregnancy to protect their babies, and few women smokers admit to smoking during pregnancy if they do. Furthermore, ethics prohibits providing cigarettes to any human being for the purpose of an experimental study. Therefore, the available data are scarce or only obtained through tests on experimental animals.

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Studies on experimental animals have shown that the acute administration of nicotine affects the ventilatory response to oxygen. Although the results are controversial, the apparent negative effects of smoking on fetuses and newborns cannot be ignored.

What Research Has Been Done?

A group of researchers from Norway, a country with a high rate of women smokers, decided to analyze the consequences of smoking during pregnancy on the respiratory system of babies. This new study, entitled “Development of Oxygen Sensitivity in Infants of Smoking and Non-smoking Mothers,” aims to evaluate the effect of prenatal exposure to cigarette smoke on postnatal restoration of oxygen sensitivity in full-term infants.

Fifteen healthy infants of smoking mothers (who smoked a median of ten cigarettes per day) and sixteen control-group infants were studied during quiet sleep at one, three, and ten days as well as ten weeks after birth. Respiratory patterns and strain-gauge trace were continuously recorded. Measurements were carried out after exposing children to high- or low-oxygen concentrations transiently through a mask, and their responses to hypoxia and hyperoxia were calculated and studied.

Controversial Results

While breathing, smoke-exposed infants had higher respiratory rates and lower displaced air during inhalation and exhalation than infants in the control group. Nicotine concentration in infant hair, measured by gas chromatography techniques, was positively linked to the level of maternal smoking. However, both groups demonstrated a more developed oxygen sensitivity in the long-term, and furthermore, the magnitude of oxygen responses was not affected by maternal smoking.

This study showed that ventilatory responses to transient hyperoxia and hypoxia continue to develop for several weeks after birth, regardless of whether the mother is a smoker or not. In healthy infants exposed to moderate levels of maternal smoking, this development is not affected.

Smoking Is Still Bad

Despite these results, previous studies have shown that high levels of nicotine in the mother negatively affect the baby. The fact that the study referred to in this text does not prove that cigarette smoking adversely affects the respiratory system of infants does not mean that there are no respiratory consequences. In fact, the researchers who conducted the study admit to certain issues that could affect the final results, such as the exclusion of heavy-smoking mothers and the selection of healthy, full-term children for the study even though women who smoke habitually often have small, sick, and preterm infants.

The reality is that cigarettes greatly harm infants’ health, affecting their growth, cardiovascular function, and probably their respiratory function. Evidence of this abounds, and the recommendation to not smoke during pregnancy is part of basic prenatal care. Obstetricians and pediatricians can provide valuable information to help mothers quit smoking.


Søvik, Signe, Kristin Lossius, Morten Eriksen, Jens Grøgaard, and Lars Walløe. “Development of oxygen sensitivity in infants of smoking and non-smoking mothers.” Early human development 56, no. 2-3 (1999): 217-232. Retrieved from https://www.sciencedirect.com

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