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A fascinating study from July 2021 focused on a possible connection between pollution during pregnancy and the growth of newborn babies. It discovered interesting relationships to a baby’s thyroid health. The study looked at how much thyroxine (a hormone produced by the thyroid) was present in newborn babies because past studies have shown that air pollution can impact the thyroid. That is why Amaia Irizar-Loibide, a researcher in the UPV/EHU’s Department of Preventive Medicine and Public Health zeroed in on the possible effects on a newborn’s thyroid levels. (1)

Air Pollution and Pregnancy Background

Thyroid hormones play a crucial role in the regulation of fetal growth and metabolism. They are also vital to neurological development. When newborns reach the 48-hour milestone, they are tested for thyroxine and TSH levels in the blood. If imbalances are present, the newborn is at increased risk for developing serious diseases. (1)

NO2 Air Pollution and Pregnancy

Nitrogen dioxide (NO2) in hand with fine particulate matter are the main pollutants in the air. (2) These pollutants are common as they are caused by traffic. Particulates smaller than 2.5 micrometers in diameter (PM2.5) can easily enter the respiratory tract. 

“In this work, we specifically analyzed the effect of maternal exposure to these fine particles and to nitrogen dioxide during pregnancy and the link existing with thyroxine levels in newborn babies,” says Irizar-Loibide. “We have been monitoring on a weekly basis, as the development of the fetus varies greatly from one week to the next. So we tried to conduct the most detailed research possible in order to find out which the most sensitive weeks of pregnancy are.” (1)

Direct Relationship Between Air Pollution and Pregnancy

“The results obtained in this study have revealed the direct relationship between exposure to fine particles during pregnancy and the level of thyroxine in newborns. However, we have not observed a clear link with exposure to nitrogen dioxide,” says Irizar-Loibide. These findings are similar to previous research on pollution. (1)

Air Pollution And Pregnancy During Early and Late Periods

The study concluded that the most sensitive periods of pregnancy are in both the early and later months when looking at the effects of atmospheric pollution. 

“What we have seen in this work is that exposure during the first months of pregnancy has a direct influence on the balance of thyroid hormones. These babies tend to have a lower level of thyroxine,” explains Irizar-Loibide. “As the pregnancy progresses, we found that this relationship gradually diminishes, i.e. the mother’s exposure gradually becomes less important. In late pregnancy, however, this link becomes apparent again, but displays an opposite effect: as the concentration of these fine particles increases, we have seen that the level of thyroid hormones also increases, which has the opposite effect on the balance.”

Further Studies on Air Pollution and Pregnancy

“The next task would be to study the mechanisms by which these fine particles cause opposing effects in early and late pregnancy,” says Irizar-Loibide. “In fact, these particles are nothing more than small spheres made up of carbon, and it is not clear whether the effect these spheres exert is because they pass from the placenta to the baby, whether other components attached to the particles are released once they have entered the body.” (1)

Irizar-Loibide believes they need to further the investigation to determine how pollution exposure during pregnancy affects neuropsychological development, growth, obesity, and more. (1) 

If you would like to get information to ensure optimum health during pregnancy, check out Dr. Nandi’s Newsletter.


  1. https://www.sciencedaily.com/releases/2021/07/210702154327.htm 
  2. https://pubmed.ncbi.nlm.nih.gov/34253165/

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