A new study from the National Institutes of Health (NIH) may shed light on why the virus has rarely been found in fetuses and newborns of mothers infected with COVID-19.
According to the study, the placental membranes that contain the fetus and amniotic fluid do not have the messenger RNA (mRNA) molecule required for ACE2 receptor manufacturing. The ACE2 receptor, as previous studies have shown, is the main cell surface receptor the virus uses to cause infection.1
The virus also requires an enzyme, TMPRSS2, to enter a cell. The placental tissues also lack mRNA needed to create the enzyme.
Researchers note that both the receptor and enzyme are present in the placenta, but in miniscule amounts, thus the absence of the virus in fetuses or newborns of mothers with COVID-19.
The researchers also found large amounts of receptors used for infection by Zika virus and cytomegalovirus in the placenta. As previous research has shown, both are known to present serious health risks when passed from mother to baby in pregnancy.