Placenta protection from COVID-19 for unborn babies

23 Nov 2021, 4:20 p.m.

Paolo de Coppi

Unborn babies are mostly protected from COVID-19 by the placenta, but may become infected if their gut is exposed to the SARS-CoV-2 virus, finds a new study led by doctors and scientists and Great Ormond Street Hospital (GOSH) and UCL Great Ormond Street Institute of Child Health, (UCL GOS ICH), led by Professor Paolo De Coppi (pictured above).

Professor De Coppi, Paediatric surgeon at GOSH and Head of Stem Cells and Regenerative Medicine at UCL GOS ICH in London, co-senior author of the study said:

“This work shows the power of collaboration between leaders in research – for the first time we are starting to understand how the placenta might ‘protect’ the unborn child from COVID-19 in the mother and how children can build up their own antibodies to coronavirus in the womb. Understanding the role of the placenta as the ‘filter’ to avoid the fetuses getting infected helps to reveal how mother and baby’s bodies ‘interact’ during pregnancy."

"We are focusing on this interaction at various levels and these laboratory-based studies have helped inform other clinical areas like surgery, where we are breaking new ground in fetal surgery, where we operate without delivering the baby.

"This work took place in state-of-the-art facilities at the Zayed Centre for Research, allowing us to access all stages of research in one building, from cell selection to cell analyses in world-class facilities.”

Research study details

The study published in ‘An International Journal of Obstetrics & Gynaecology’ (BJOG) seeks to understand how newborn babies could have developed COVID-19 antibodies, as has been documented in a small number of cases.

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.

Co-senior author, Dr Mattia Gerli (UCL Division of Surgery and Interventional Science & the Royal Free Hospital) explained: “The fetus is known to begin swallowing the amniotic fluid in the second half of pregnancy. To cause infection, the SARS-CoV-2 virus would need to be present in significant quantities in the amniotic fluid around the fetus.

“However, many studies in maternity care have found that the amniotic fluid around the fetus does not usually contain the SARS-CoV2 virus, even if the mother is infected with Covid-19. Our findings therefore explain that clinical infection of the fetus during pregnancy is possible but uncommon and that is reassuring for parents-to-be.”

The study, funded by the Medical Research Council (MRC) and UKRI COVID-19 rapid response initiative, provides the most definitive information, to date, regarding the susceptibility of the human fetus to COVID-19 infection.

Co-author, Professor Anna David (UCL Elizabeth Garrett Anderson Institute for Women’s Health and UCLH NIHR Biomedical Research Centre) added: “Vaccination against Covid-19 is known to be safe in pregnancy and reduces the chance of Sars-CoV2 infection to very low levels. The results of this study provide definitive information regarding the susceptibility of the human fetus to Covid-19 infection. Our findings support current healthcare policy that vaccination in pregnancy is the best way for mothers to protect their unborn baby from Covid-19 infection.”

*The researchers did not find evidence of the receptors ACE2 and TMPRSS2 in the fetal lung or placenta in the middle or last trimester of pregnancy. The results were confirmed using a number of different techniques, including looking for both gene and protein expression. 

Authors: MA Beesley, JR Davidson, F Panariello, S Shibuya, D Scaglioni, BC Jones, K Maksym, O Ogunbiyi, NJ Sebire, D Cacchiarelli, AL David, P De Coppi, MFM Gerli.

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