Pregnant women with SARS-CoV-2 infection are unlikely to transmit the virus to their newborn, but anti-SARS-CoV-2 antibodies may not be transferred easily either, according to a study. Dr. Andrea Edlow from Massachusetts General Hospital in Boston and colleagues studied 127 pregnant women in their third trimester who received care at three Boston hospitals between April 2 and June 13. Sixty-four women were positive for SARS-CoV-2 by RT-PCR and 63 were negative for the virus. Of the women with SARS-CoV-2 infection, 23 (36%) were asymptomatic, 22 (34%) had mild disease, seven (11%) had moderate disease, 10 (16%) had severe disease and two (3%) had critical disease. There was no virus detected in maternal or cord blood, no signs of the virus in placentas and no evidence of viral transmission to newborns, the researchers report in JAMA Network Open. Most of the women with SARS-CoV-2 infection developed antibodies against SARS-CoV-2, but mother-to-newborn transfer of anti-SARS-CoV-2 antibodies through the placenta was "inefficient" and significantly lower than transfer of anti-influenza antibodies, the researchers report. Reduced transplacental transfer of anti-SARS-CoV-2 antibodies may increase the risk of SARS-CoV-2 infection for neonates and infants, the researchers note. The authors of an editorial say the inefficient transfer of SARS-COV-2 maternal antibodies to the infant, in contrast to vaccine-induced influenza antibodies is a "major finding." "A critical benefit to vaccinating pregnant women for influenza is that the vaccine protects the infant for several months after birth by the transplacental transfer of anti-influenza-specific serum immunoglobulin G. In this way, antenatal vaccination helps protect not only the mother but also provides neonatal protection," note Dr. Denise Jamieson of Emory University School of Medicine, in Atlanta, and Dr. Sonja Rasmussen of the University of Florida College of Medicine, in Gainesville. "Although it is not known whether the inefficient transplacental transfer of antibodies observed by Edlow et al will also extend to antibodies elicited by future SARS-CoV-2 vaccines, it underscores the susceptibility of infants, particularly since it is unlikely that young infants will be eligible for SARS-CoV-2 vaccination," they write. "While children have been shown to be more mildly affected by SARS-CoV-2 infection compared with adults, infants are at higher risk for severe coronavirus disease 2019 (COVID-19) than children of other ages. The study by Edlow et al adds important information to our understanding of vertical transmission and raises concerns about the lack of impact that a vaccine given to women during pregnancy might have on protecting neonates. It also highlights the importance of protecting pregnant women and their newborns from exposure to SARS-CoV-2 infection," the editorial writers conclude. Dr. Edlow did not respond to a request for comment by press time. —Megan Brooks Source
