The potential for mothers to pass the new coronavirus, which causes COVID-19, on to their babies “cannot be ruled,” according to the authors of a study.
Although more research is needed, a small study, published in the journal JAMA Pediatrics on Thursday, found that of 33 women in China who were confirmed to have the coronavirus while pregnant, three gave birth to newborns who were then diagnosed with the virus. All three infants recovered, adding to a growing pile of evidence that most children experience milder cases of COVID-19, the illness caused by the coronavirus, than adults.
Babies born to the other 30 women in the study tested negative for the virus.
Because the three newborns who tested positive were diagnosed so early in life — all three received positive tests on their second day of life and again on their fourth day of life — the source of the transmission was likely “maternal in origin,” the study authors wrote.
What exactly that means is up for debate, said Dr. David Kimberlin, a professor of pediatrics at the University of Alabama at Birmingham and a pediatric infectious disease physician, who was not involved in the study.
Very few viruses cross over into the placenta and infect babies in utero, Kimberlin said, although some — like Zika — do, with devastating effects. In the coronavirus study, the newborns’ positive results, which were acquired through swab tests, “is more suggestive of the possibility of perinatal transmission around the time of delivery,” he added.
The babies could have acquired the coronavirus from the birth canal or from microtears in their amniotic sacs, among other possibilities, he said.
But because the sample size is so small, more information is needed, according to Kimberlin, who co-authored an editorial about two other papers published Thursday in the Journal of the American Medical Association about whether the coronavirus can be acquired in utero.
Those papers suggested that infants born to infected mothers can have elevated antibodies for the virus detected in their own blood, although it is not clear whether the antibodies were made in response to the infection in the womb or simply made by the mother and transferred to the baby.
The data at this point are “not conclusive and do not prove in utero transmission,” the editorial said.
The JAMA Pediatrics study offered encouraging news about infants’ ability to recover from the coronavirus. Two of the three who were infected with it no longer tested positive by the sixth day of life, and the third, who had been born prematurely, was negative by the seventh day of life.