Allergies: the role of intrauterine life

Intrauterine life influences the risk that a child will subsequently develop an allergy. How? A less rich meconium affects the development of the gut microbiota and, ultimately, the immune system.

Created 16 November 2021
Updated 02 May 2024

About this article

Created 16 November 2021
Updated 02 May 2024

While some people can read the future in coffee grounds, researchers are beginning to use (sidenote: Meconium Earliest “stool” of the newborn, containing the amniotic liquid absorbed in utero. The meconium helps identify microorganisms lining the gastrointestinal tract of the fetus.
 –  the “tarry” first stool of infants – to predict the risk of developing allergies. Eczema, food allergies, asthma, allergic rhinitis: today, nearly one in three children suffers from an allergy. However, many things may be at play even before birth. Hence researchers had the idea of studying meconium, which begins forming in utero by gestational week 16. 

Signs of allergy even during pregnancy?

Their results support the idea that the onset of an allergy begins well before the first symptoms appear: at three months of age, future allergic infants have a less diverse and less mature gut microbiota than peers. The researchers therefore looked back in time, at their very first stool, the much-vaunted meconium: the same observation was made, a lower diversity of bacteria and a low diversity of molecules produced by these microorganisms. The appearance of an allergy may therefore be explained by the following mechanism: during pregnancy, environmental factors favoring an allergy modify the composition of the meconium, which is less rich in metabolites at birth. Since the first bacteria to colonize the infant’s digestive tract feed on these metabolites, a less rich meconium means the microbiota is less diverse and matures more slowly early in life. 

Prevent... and predict?

These discoveries have multiple implications. On the one hand, the researchers hope one day to be able to prevent these allergies. This will require a better understanding not only of what affects the composition of meconium in utero, but also of how the different metabolites of meconium influence bacterial colonization in newborns. At the same time, they hope to be able to predict the risk of developing an allergy based on the composition of a newborn’s meconium. In the meantime, the only recommendation to be made is for women to adopt a healthy lifestyle during pregnancy.

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