Mpox Virus in Pregnancy, the Placenta, and Newborn.

David A Schwartz, Sandy Ha, Pradip Dashraath, David Baud, Phillip R Pittman, Kristina Adams Waldorf

Before its eradication, the smallpox virus was a significant cause of poor obstetrical 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. 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. The data are obtained from the authors cases and from various published sources, including early historical information and contemporary publications. 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, there have been increasing numbers of pregnant women infected with the virus. A detailed description of the Congenital Mpox Syndrome in a stillborn resulting from maternal-fetal transmission and placental infection is described, and the potential mechanisms of intrauterine infection are discussed. Other poxviruses, notably vaccinia virus and, in one 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.