Mpox a Cause for Concern in Pregnant Persons

Contracting the monkeypox virus (mpox) while pregnant can cause Congenital Mpox Syndrome, placental infection, and stillbirth, according to an article posted online in Archives of Pathology & Laboratory Medicine, the scientific journal published by the College of American Pathologists (CAP).

Now known as mpox, this poxvirus is related to the now-eradicated smallpox virus. Mpox was known to infect pregnant persons in Africa, producing a 75 percent perinatal fatality rate.

David A. Schwartz, MD, MS Hyg, FCAP, a leading perinatal and infectious disease pathology expert, together with five colleagues, evaluated the pathophysiology of mpox in pregnancy, comparing it with smallpox and other poxviruses. They provide insight about how mpox can infect the fetus and describe details of a stillborn with placental infection, define and illustrate the Congenital Mpox Syndrome, and discuss mechanisms of intrauterine mpox transmission.

Dr. Schwartz and colleagues say that mpox has the ability to reach and then cross the placenta to infect the fetus prior to delivery following spread of the virus through the mother's bloodstream. "The description of a stillborn fetus having placental infection with mpox, characteristic skin lesions, an enlarged liver, increased body fluids, and molecular pathology confirmation of mpox in both maternal and fetal tissues, constitutes the Congenital Mpox Syndrome," explains Dr. Schwartz. "This adds mpox to a list of other viral diseases that can cause placental infection and stillbirth including COVID-19, Zika, Ebola, cytomegalovirus, and others."

Mpox had essentially been restricted to Central and West Africa. Starting in May 2022, mpox was identified outside of these endemic areas, and rapidly spread globally. Although most mpox infections occurred in men, cases in women have increased, resulting in an intense concern for pregnant individuals acquiring the infection.

As of February 15, 2023, 30,193 cases of mpox occurred in the United States. The U.S. Centers for Disease Control and Prevention reported on November 7^th, 2022, that 23 cases of mpox were associated with pregnancy. In Brazil, 22 pregnant persons with mpox have been reported. Several newborns have developed mpox following delivery, likely representing exposure during, or following delivery.

"With the demonstration of intrauterine and postpartum infections from mpox, we can expect that we will see additional cases of perinatal disease," states Dr. Schwartz. "The current outbreak has demonstrated the need for increased research on this most dangerous of poxviruses to human health. Healthcare providers should be aware that mpox occurring in pregnant persons is uncommon but has the capability to infect the fetus as well as the newborn and cause both perinatal morbidity and mortality."

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