Hematogenous infections of the placenta—An interdisciplinary and evolutionary perspective

Mpox Virus in Pregnancy, the Placenta, and Newborn

CONTEXT.—

Before its eradication, the smallpox virus was a significant cause of poor obstetric outcomes, including maternal and fetal morbidity and mortality. The mpox (monkeypox) virus is now the most pathogenic member of the Orthopoxvirus genus infecting humans. The 2022 global mpox outbreak has focused attention on its potential effects during pregnancy.

OBJECTIVE.—

To understand the comparative effects of different poxvirus infections on pregnancy, including mpox virus, variola virus, vaccinia virus, and cowpox virus. The impact on the pregnant individual, fetus, and placenta will be examined, with particular attention to the occurrence of intrauterine vertical transmission and congenital infection.

DATA SOURCES.—

The data are obtained from the authors' cases and from various published sources, including early historical information and contemporary publications.

CONCLUSIONS.—

Smallpox caused maternal and perinatal death, with numerous cases reported of intrauterine transmission. In endemic African countries, mpox has also affected pregnant individuals, with up to a 75% perinatal case fatality rate. Since the start of the 2022 mpox outbreak, increasing numbers of pregnant women have been infected with the virus. A detailed description is given of the congenital mpox syndrome in a stillborn fetus, resulting from maternal-fetal transmission and placental infection, and the potential mechanisms of intrauterine infection are discussed. Other poxviruses, notably vaccinia virus and, in 1 case, cowpox virus, can also cause perinatal infection. Based on the historical evidence of poxvirus infections, mpox remains a threat to the pregnant population, and it can be expected that additional cases will occur in the future.

Confirming Vertical Fetal Infection With Coronavirus Disease 2019: Neonatal and Pathology Criteria for Early Onset and Transplacental Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 From Infected Pregnant Mothers

Increasing numbers of pregnant women with coronavirus disease 2019 are being reported around the world. The majority of neonates delivered to pregnant women infected with severe acute respiratory syndrome coronavirus 2 have been negative for the virus, but a small number have tested positive for infection. It is important to determine whether vertical transmission of coronavirus disease 2019 occurs and the mechanisms for its development. Based on a number of clinical and laboratory findings, it has been suggested that transplacental transmission may be occurring, but a method to confirm this is necessary. This communication analyzes and evaluates the covariables that have been discussed as potential indicators of vertical and, specifically, intrauterine transmission, including the timing of onset of neonatal illness, neonatal viral test positivity, neonatal antibody testing for immunoglobulin (Ig) G and IgM, and viral analysis of swabs of whole specimens of placental tissue. None of these methods can provide confirmatory evidence that infection developed prior to labor and delivery, or that transplacental transmission occurred. This commentary proposes that diagnosis of early-onset neonatal coronavirus disease 2019 infection should be limited to neonates with positive reverse transcription polymerase chain reaction testing for severe acute respiratory syndrome coronavirus 2 within the initial 72 hours of life. It also proposes that the occurrence of intrauterine transplacental severe acute respiratory syndrome coronavirus 2 among infected mother-infant dyads be based upon identification of severe acute respiratory syndrome coronavirus 2 in chorionic villus cells using immunohistochemistry or nucleic acid methods such as in situ hybridization. Evaluating placentas from neonates with coronavirus disease 2019 using these methods will be instrumental in determining the potential role and prevalence of transplacental transmission of the coronavirus.

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.