One of the many big questions that scientists are trying to unravel is whether people who take Covid-19 during pregnancy transmit some natural immunity to their newborns.
Recent studies have suggested that yes. And new findings, published on Friday in the journal JAMA Pediatrics, provide another piece of the puzzle, offering more evidence that Covid-19 antibodies can cross the placenta.
“What we found is very consistent with what we learned from studies of other viruses,” said Scott E. Hensley, associate professor of microbiology at the University of Pennsylvania’s Perelman School of Medicine and a leading study author.
In addition, he added, the study suggests that women are not only transferring antibodies to their fetuses, but also transferring more antibodies to their babies if they become infected in early pregnancy. This may have implications for when women should be vaccinated against Covid-19, said Hensley, adding that vaccinating women in early pregnancy may offer more protective benefits, “but studies that really look at vaccination among pregnant women need to be completed” .
In the study, Pennsylvania researchers 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 were found to have antibodies to Covid-19 – and after they gave birth, 72 of these babies tested positive for antibodies to Covid-19 through umbilical cord blood, regardless of whether their mothers had symptoms.
According to Dr. Karen Puopolo, associate professor of pediatrics at the University of Pennsylvania and one of the study’s senior authors, about half of these babies had antibody levels as high or higher than those found in their mothers’ blood, and in about a quarter of cases, cord blood antibody levels were 1.5 to 2 times higher than the mother’s concentrations.
“This is very efficient,” said Puopolo.
The researchers also noted that the longer the time between the onset of Covid-19 infection in a pregnant woman and her delivery, the more antibodies were transferred, a finding that has been observed elsewhere.
The antibodies that crossed the placenta were immunoglobulin G, or IgG, antibodies, the type that is made days after infection and is believed to offer long-term protection against the coronavirus.
None of the babies in this study had immunoglobulin M antibodies, or IgM, which are usually detected shortly after an infection, suggesting that the babies were not infected with the coronavirus.
Experts still do not know whether the amount of antibodies transmitted to babies was sufficient to prevent newborns from contracting Covid-19. And because only a few of the babies in the study were born prematurely, the researchers cannot say whether babies who are born early can lose these protective antibodies. The study authors also noted that, as their results were from just one installation, the findings would need to be replicated later.
The placenta is a complex and poorly studied organ, said Dr. Denise Jamieson, an obstetrician at Emory University in Atlanta and a member of the Covid group of experts at the American College of Obstetricians and Gynecologists, which was not involved in the study.
And more research is needed to better understand whether antibodies generated by the vaccine behave in a comparable way to antibodies from Covid-19 infection, said Dr. Andrea G. Edlow, assistant professor of obstetrics, gynecology and reproductive biology at Harvard Medical School .
In a study published in the journal Cell in December, for example, Dr. Edlow and her colleagues found that Covid-19 antibodies from a natural infection can cross the placenta less efficiently than antibodies produced after vaccination against influenza and whooping cough. (whooping cough).
“What we really want to know is whether the antibodies in the vaccine cross the placenta efficiently and protect the baby, the way we know it happens in flu and whooping cough,” said Dr. Jamieson.
Experts do not know whether the Covid vaccine will work that way, in part because pregnant women have been excluded from initial clinical trials.
“It is plausible that the Covid vaccine offers protection for pregnant mothers and their babies,” said Dr. Mark Turrentine, a member of the Covid expert group at ACOG “For me,” he added, “this study highlights the inclusion of pregnant women in clinical trials, such as the Covid-19 vaccine, it is essential, especially when the benefit of vaccination is greater than the potential risk of a life-threatening disease. “