Coronavirus Diseases in Pregnant Women, the Placenta, Fetus, and Neonate.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), the etiological agent of coronavirus disease 2019 (COVID-19), is similar to two other coronaviruses, severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), in causing life-threatening respiratory infections and systemic complications in both children and adults. As the COVID-19 pandemic has continued to spread globally, increasing numbers of pregnant women have become infected, raising concern not only for their health but also for the health of their infants. This chapter discusses the effects of coronavirus infections, e.g., MERS, SARS, and COVID 19, on pregnancy and describes the evolving knowledge of COVID 19 among pregnant women. The physiological changes that occur in pregnancy, especially changes in the immune system, are reviewed in terms of their effect on susceptibility to infectious diseases. The effects of COVID-19 on the placenta, fetus, and neonate are also reviewed, including potential clinical outcomes and issues relating to testing and diagnosis. The potential mechanisms of vertical transmission of the virus between pregnant women and their infants are analyzed, including intrauterine, intrapartum, and postpartum infections. Several recent studies have reported the detection of SARS-CoV-2 in tissues from the fetal side of the placenta, permitting the diagnosis of transplacental infection of the fetus by SARS-CoV-2. Placentas from infected mothers in which intrauterine transplacental transmission of SARS-CoV-2 has occurred demonstrate an unusual combination of pathology findings which may represent risk factors for placental as well as fetal infection.

INFECTIONS IN PREGNANCY WITH COVID-19 AND OTHER RESPIRATORY RNA VIRUS DISEASES ARE RARELY, IF EVER, TRANSMITTED TO THE FETUS: EXPERIENCES WITH CORONAVIRUSES, HPIV, hMPV RSV, AND INFLUENZA.

SARS-CoV-2, the agent of COVID-19, is similar to two other coronaviruses, SARS-CoV and 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 COVID-19 or any other coronavirus infections. Influenza virus, despite causing approximately one billion annual infections globally, has only a few cases of confirmed or suspected intrauterine fetal infections reported. RSV is in an unusual cause of illness among pregnant women, and with the exception of one premature infant with congenital pneumonia, no other cases of maternal-fetal infection are described. Parainfluenza virus and human metapneumovirus can produce symptomatic maternal infections but do not cause intrauterine fetal infection. In summary, it appears that the absence thus far of maternal-fetal 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 as it appears that if intrauterine transmission of SARSCoV-2 does eventually occur, it will be a rare event. Potential mechanisms of fetal protection from maternal viral infections are also discussed.