Infections in Pregnancy With COVID-19 and Other Respiratory RNA Virus Diseases Are Rarely, If Ever, Transmitted to the Fetus Experiences With Coronaviruses, Parainfluenza, Metapneumovirus Respiratory Syncytial Virus, and Influenza

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the agent of coronavirus disease 2019 (COVID19), is similar to 2 other coronaviruses, SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV), in causing life-threatening maternal respiratory infections and systemic complications. Because of global concern for potential intrauterine transmission of SARS-CoV-2 from pregnant women to their infants, this report analyzes the effects on pregnancy of infections caused by SARS-CoV-2 and other respiratory RNA viruses, and examines the frequency of maternal-fetal transmission with SARS-CoV-2, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), influenza, respiratory syncytial virus (RSV), parainfluenza (HPIV), and metapneumovirus (hMPV). There have been no confirmed cases of intrauterine transmission reported with SARS-CoV-2 or any other coronaviruses-SARS and MERS. Influenza virus, despite causing approximately 1 billion annual infections globally, has only a few cases of confirmed or suspected intrauterine fetal infections reported. Respiratory syncytial virus is an unusual cause of illness among pregnant women, and with the exception of 1 premature infant with congenital pneumonia, no other cases of maternal-fetal infection are described. Parainfluenza virus and hMPV can produce symptomatic maternal infections but do not cause intrauterine fetal infection. In summary, it appears that the absence thus far of maternalfetal transmission of the SARS-CoV-2 virus during the COVID-19 pandemic is similar to other coronaviruses, and is also consistent with the extreme rarity of suggested or confirmed cases of intrauterine transmission of other respiratory RNA viruses. This observation has important consequences for pregnant women because it appears that if intrauterine transmission of SARS-CoV-2 does eventually occur, it will be a rare event. Potential mechanisms of fetal protection from maternal viral infections are also dis- cussed.