A pregnant woman’s placenta acts as a barrier to the Covid-19 virus, protecting the foetus, according to research by the university of Louvain-la-Neuve and the Saint-Luc university clinic.
The placenta is an unusual organ, in that it only grows during pregnancy, its purpose to provide oxygen and nutrients to the foetus, while cleaning its blood and carrying away waste products.
The team studied cells from the placenta of pregnant women who had contracted Covid-19 during the third trimester of their pregnancy.
“We looked at placental cells which have the particularity of reproducing in culture and reproducing the interface between the mother and the fetus. We then exposed these cells to the virus, which had never been done before," said Dr Arthur Colson, co-author of the study.
The cells, he said, were literally bombarded with virus, to an extent impossible in nature, in order to test the cells to destruction.
The experiment confirmed that it is extremely rare for the virus to affect the placenta from the third trimester, beginning at about 27 weeks.
"We observed that the placenta cannot technically be infected with SARS-CoV-2 because the virus lacks half of the key needed to enter the placental cell," Dr Colson told the RTBF.
The major difference is with the lung, the main portal for the virus to enter the body. Lung tissue contains the receptors used by the virus, which are not present in placental cells.
And even when the team was able to grow placental cells in vitro which did contain receptors, the virus was still powerless to enter.
However, Dr Colson stressed that the research provides reassurance only to women infected with Covid in the third trimester. Until then, pregnant women remain vulnerable.
The point was backed by Professor Frédéric Debiève, head of obstetrics at Saint-Luc.
"The virus does not reach the unborn child. That is reassuring for pregnant women. Nevertheless, a pregnant woman who has Covid-19 is exposed to high temperatures, respiratory distress, all of which can also have consequences for the baby,” he said.
“Even if the virus does not directly reach the baby because the placenta protects it, it remains exposed to the consequences of the disease in its mother and therefore precautions must be taken for pregnant women. Vaccination is the first of the precautions."