Can a pregnant woman transmit Covid-19 to the fetus? It is likely, but relatively unusual, and scientists think they know why.
Many viruses can cross the placenta and infect the fetus in utero, and there is growing evidence that the coronavirus can sometimes do so as well.
Researchers in Italy, they studied 31 women with Covid-19 who gave birth in March and April and found signs of the virus in several blood samples from the umbilical cord, the placenta and in one case in breast milk. But this kind of test can only detect traces of genetic material: it does not mean the presence of a virus capable of causing infection in those places.
In one case, tests indicated that the newborn had the virus at birth because they were found signs in the umbilical cord blood and in the placenta. In another, the newborn had certain antibodies to the coronavirus unable to cross the placenta, so they could not come from the mother.
A French report presented even stronger evidence of infection in the uterus, and the newborn was very ill at birth.
Meanwhile, research by the National Institutes of Health indicated why fetuses do not spread more frequently: placental cells rarely make the two tools that the coronavirus uses to penetrate. Instead, they found an abundance of those using Zika and other types of viruses.
Most research to date has been on women who were in the later stages of pregnancy when they contracted the disease; More research is needed for earlier infection cases.
The advice for pregnant women is the same: wear the mask in public, wash your hands frequently, and stay at least two meters from others to avoid contagion.