Human embryos could be susceptible to Covid-19 as early as the second week of pregnancy if the mother gets sick, a new study suggests.
Researchers say their findings indicate it may be possible that coronavirus could affect the ability of the embryo to properly implant into the womb, or have implications for future foetal health.
The study, which uses gene expression data only, found the genes for proteins that make cells susceptible to infection by the virus are expressed in the embryo in the first 14 days of development.
These are important stages in development when the embryo attaches to the mother’s womb and undertakes a major remodelling of all of its tissues.
Gene expression is the process by which specific genes are activated to produce a required protein.
Genes encode proteins and proteins dictate cell function, and the thousands of genes expressed in a particular cell determine what it can do.
However, the scientists highlight that their findings have not been validated at the protein level, in stem cell embryo models or animal models.
The study does not show that SARS-CoV-2 virus either does or is more likely to infect embryo cells, but it suggests there is a potential route through which it might.
Writing in the Open Biology journal, Professor David Glover from the University of Cambridge, and colleagues, say: “Our present study offers an indication that the potential effect of SARS-CoV-2 infection on the early embryo should be further investigated using both stem cell models of the embryo and in the mouse.”
But experts say even if mothers are infected, transmission of the virus to the baby is unlikely, and even if the baby does become infected the outcomes are generally good.
Christoph Lees, professor of obstetrics, Imperial College London, said: “This is an intriguing laboratory based study using newly developed culture platforms that enable researchers to look at the expression of genes in the early human embryo.
“Some genes may be implicated in how the SARS-CoV-2 virus enters cells.
“The study finds that these genes might be present at a very early stage and raises the possibility – if this were the case – that the embryo might be susceptible to the virus.
“It is important to say that this work is at a very hypothetical stage – in other words, there are more question marks than there are answers.”
He adds that what appears possible in a laboratory study is a long way removed from what might actually happen in the human embryo.
Prof Lees also says it is important to note there has been been no evidence of an increased risk of miscarriage or other foetal problems from the tens of pregnancies that we know have been exposed to Covid-19 so far.
Andrew Shennan, professor of obstetrics at the department of women and children’s health, King’s College London, said: “This work is well conducted science research that suggests the cells of babies in the womb can be infected by coronavirus in early pregnancy if they are exposed to the virus.
“However, an increasing evidence base suggests it is rare for the virus to cross the placenta in pregnancy.
“Even if foetal cells are infected, this research does not indicate they would be harmed. Most cells make a complete recovery after being infected with a virus.”