An unborn baby could become infected with Covid-19 if their gut is exposed to the SARS-CoV-2 virus, finds a new study led by UCL researchers with Great Ormond Street Hospital for Children and the NIHR Great Ormond Street Biomedical Research Centre.

Although the study did not look specifically at mothers with Covid-19 and whether their infection was transmitted to an unborn baby, it found that certain fetal organs, such as the intestine, are more susceptible to infection than others.

However, researchers say, that opportunities for the Covid-19 virus infecting the fetus are extremely limited, as the placenta acts as a highly effective and protective shield, and evidence suggests fetal infection, known as vertical transmission, is extremely uncommon.

For the study, published in BJOG: An International Journal of Obstetrics & Gynaecology, researchers set out to understand how newborn babies could have developed Covid-19 antibodies, as has been reported in a small number of cases.

Specifically, they wanted to know if and how the virus could be passed from an infected mother to the unborn fetus.

To answer this question, researchers examined various fetal organs and placenta tissue to see if there was any presence of the cell surface protein receptors, ACE2 and TMPRSS2. These two receptors sit on the outside of cells and both are needed for the SARS-Cov-2 virus to infect and spread.

Researchers found the only fetal organs* to feature both the ACE2 and TMPRSS2 were the intestines (gut) and the kidney; however the fetal kidney is anatomically protected from exposure to the virus and is therefore less at risk of infection.

Therefore, the team concluded that the SARS-CoV-2 virus could only infect the fetus via the gut and through fetal swallowing of amniotic fluid, which the unborn baby does naturally for nutrients.

After birth ACE2 and TMPRSS2 receptors are known to be present in combination on the surface of cells in the human intestine as well as the lung. The gut and lung are suspected to be the main routes for Covid-19 infection, but in younger children, the intestine appears to be most important for virus infection.

Release date: 19 November 2021
Source: University College London

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