It’s rare for mothers with COVID-19 to transfer the infection to their newborns, according to a new small study.
The research, published in JAMA Network Open, found that newborns of mothers infected with the COVID-19 virus were able to develop their own immune defenses via their mother’s breast milk. Researchers detected antibodies in the infants’ saliva.
“It is the first time that this mechanism has been demonstrated,” said study author Rita Carsetti, MD, head of immunology diagnostics for Bambino Gesù Children’s Hospital in Rome. “We now know how breast milk can help babies develop their immune defenses. The system could work the same way for many other pathogens, which are present in the mother during breastfeeding.”
Dr. Carsetti and colleagues examined data from 28 pregnant women who tested positive for COVID-19 and who gave birth at Policlinico Umberto I in Rome between November 2020 and May 2021, and their newborns. They investigated the immune responses of the mothers and their newborns by detecting spike-specific antibodies in serum, and the mucosal immune response was assessed by measuring specific antibodies in maternal breast milk and infant saliva 48 hours after delivery and 2 months later.
Twenty-one mothers and their newborns completed the 2 months of follow-up. Researchers found that the majority of the mothers had mild symptoms of COVID-19, while only three of them were admitted for worsening condition. There was only one reported case of a possible vertical transmission – transmitted in utero – and one case of a horizontal infection through droplets or respiratory secretions, which occurred when the newborn was taken home.
The results of the study showed that antibodies specific to the virus were present in the mothers’ blood at 2 months after delivery, but not at 48 hours. However, in milk, specific antibodies were already present 48 hours after delivery.
Therefore, after 48 hours, the breastfed babies had specific mucosal antibodies against COVID-19 in their saliva that the other newborns did not have. Two months later, these antibodies continued to be present even though the mothers had stopped producing them.
The findings suggest that breast milk offers protection by transferring the antibodies produced by the mother to the baby, but also by helping them to produce their own immune defenses.
“I am not surprised that infants of mothers who had COVID-19 infection in the peripartum period pass anti-spike protein IgA to their infants,” J. Howard Smart, MD, FAAP, who was not involved with the study, said in an interview. “This confirmation is good news for breastfeeding mothers.
“I wonder whether we really know these infants did not become infected, and produce their own antibodies,” said Dr. Smart, chairman of the department of pediatrics at Sharp Rees-Stealy Medical Group in San Diego.
The American College of Obstetricians and Gynecologists said having COVID-19 should not stop mothers from giving their children breast milk. The organization also said that the chance of COVID-19 passing through the breast milk and causing infection in the newborn infant is slim.
“Breast milk also helps protect babies from infections, including infections of the ears, lungs, and digestive system. For these reasons, having COVID-19 should not stop you from giving your baby breast milk,” according to ACOG’s website.
Similar studies on mothers who received the COVID-19 vaccination rather than being infected would be interesting, Dr. Smart added.
The authors of the current study plan to broaden their research by evaluating the response of pregnant mothers vaccinated against SARS-CoV-2 for the presence of antibodies in the milk and the immunity of their newborns. Dr. Carsetti said her team plans to expand the study to other infections, such as cytomegalovirus and respiratory syncytial virus.
None of the researchers or commentators had financial disclosures.