Pennsylvania issues alert on congenital measles—something US hasn't seen for decades

Risky infection

Pregnant people who have not been vaccinated against measles nor previously had the infection are susceptible. A case of measles during pregnancy increases the risk of hospitalization, pneumonia, the need for oxygen support or mechanical ventilation, and death. It also increases the risk of miscarriage, stillbirth, low birth weight, and preterm labor. The MMR vaccine is not recommended during pregnancy because it is a live attenuated vaccine and poses a theoretical risk of causing an infection in a fetus. If a pregnant person is exposed to the virus, they’re recommended to receive intravenous immunoglobulin to help protect against infection—but only if it is given within six days of exposure.

If there’s a measles infection during pregnancy, the measles virus can pass to a fetus in utero or can transmit during or just after birth, leading to a congenital case. These cases can vary widely in symptoms and severity. Some babies will remain asymptomatic while others develop severe, multisystem disease and death. Some common symptoms of congenital measles include fever and jaundice. They can also develop the telltale measles rash, but it is sometimes delayed or atypical given a newborn’s underdeveloped immune system. Other symptoms can include low platelet counts, pneumonia, and neurologic complications.

Even if a newborn survives the acute infection, they are at risk of long-term complications. These include immune amnesia, a type of immunosuppression in which the measles virus destroys immune cells and adaptive responses. They are also at risk of subacute sclerosing panencephalitis (SSPE), a progressive, fatal neurological disorder that can strike years after an infection.

The alert warns that babies with congenital measles need long-term clinical follow-up and monitoring for these neurologic and immunologic complications, and parents need counseling on how to spot early signs of SSPE, which include seizures, regression in milestones, and academic difficulties in older children.

This story was updated on October 20 to include case information from the Pennsylvania state health department.