One of the many big questions scientists are trying to unravel is whether people who receive Covid-19 while pregnant pass natural immunity to their newborns.

Recent studies have indicated that this could be the case. New findings published in JAMA Pediatrics magazine on Friday are another piece of the puzzle that provides more evidence that Covid-19 antibodies can cross the placenta.

“What we found agrees pretty well with what we learned from studies with other viruses,” said Scott E. Hensley, associate professor of microbiology at the Perelman School of Medicine at the University of Pennsylvania and a leading author of the study.

In addition, the study suggests that women not only transfer antibodies to their fetuses, but also transfer more antibodies to their babies if they are infected earlier in pregnancy. This could have an impact on when women should be vaccinated against Covid-19, said Dr. Hensley, adding that vaccinating women earlier in pregnancy could provide more protective benefits, “but studies that actually analyze vaccination in pregnant women need to be completed.”

In the study, researchers from Pennsylvania tested more than 1,500 women who gave birth at the Pennsylvania Hospital in Philadelphia between April and August last year. Of these, 83 women had Covid-19 antibodies – and after birth, 72 of these babies tested positive for Covid-19 antibodies through their umbilical cord blood, regardless of whether their mothers had symptoms.

According to Dr. Karen Puopolo, an associate professor of pediatrics at the University of Pennsylvania and one of the study’s lead authors, found that about half of these babies had antibody levels that were as high or higher than those found in their mother’s blood, and about a quarter of the cases were Antibody levels in umbilical cord blood 1.5 to 2 times higher than the concentrations in the mother.

“That’s pretty efficient,” said Dr. Puopolo.

The researchers also observed that the longer the time span between a pregnant woman’s onset of Covid-19 infection and her delivery, the more antibodies were transferred, a finding noted elsewhere.

Updated

Jan. 29, 2021, 9:34 p.m. ET

The antibodies that crossed the placenta were immunoglobulin G or IgG antibodies made a few days after infection and believed to provide long-term protection against the coronavirus.

None of the babies in this study were found to have immunoglobulin M or IgM antibodies, which are typically not detected until soon after infection, suggesting that the babies were not infected with the coronavirus.

Experts don’t yet know if the amount of antibodies passed on to the babies was enough to prevent newborns from getting Covid-19. And because only some of the babies in the study were born prematurely, the researchers can’t say whether premature babies might miss these protective antibodies. The study’s authors also noted that the findings needed further replication as their findings only came from one facility.

The placenta is a complex and under-studied organ, said Dr. Denise Jamieson, an obstetrician at Emory University in Atlanta and a member of the Covid Expert Group at the American College of Obstetricians and Gynecologists who was not involved in the organ study.

More research is needed to better understand whether antibodies generated by vaccines behave similarly to antibodies against Covid-19 infections, said Dr. Andrea G. Edlow, Assistant Professor of Obstetrics, Gynecology, and Reproductive Biology at Harvard Medical School.

In a study published in Cell in December, Dr. For example, Edlow and her colleagues found that Covid-19 antibodies, due to a natural infection, may cross the placenta less efficiently than antibodies produced after vaccination against flu and whooping cough (pertussis). .

“What we really want to know is that antibodies from the vaccine efficiently cross the placenta and protect the baby as we know it to do with influenza and pertussis,” said Dr. Jamieson.

Experts don’t know if the Covid vaccine works this way, partly because pregnant women were excluded from the initial clinical trials.

“It is plausible that the Covid vaccine will offer protection to both pregnant mothers and their infants,” said Dr. Mark Turrentine, member of the Covid expert group at ACOG. “For me,” he added, “this study highlights the inclusion of pregnant women. Women in clinical trials such as the Covid-19 vaccine are critical, especially when the benefits of vaccination outweigh the potential risk of life-threatening illness. “