A new health alert of the Pennsylvania Department of Health is warning doctors about congenital measles, a disease once extremely rare in the United States. But now that dozens of pregnant Pennsylvania women have contracted measles during the state’s ongoing outbreak, the potentially deadly infection passed from mother to baby in utero is poised to pose clinical challenges for doctors confronting a disease they’ve never seen in practice.
So far, Pennsylvania has reported that 66 pregnant women have contracted measles during pregnancy this year, and at least six babies in the state were born with measles. Of the six deaths reported in the state, at least two were infants, but it is unclear whether they suffered from congenital infections.
Publishing information about the outcomes of these infant pregnancies is illegal in Pennsylvania. According to NBC News, there is also no national database for congenital measles, likely because the disease has not been seen regularly in the United States for decades.
No “denominator data”
“We don’t have denominator data on congenital measles,” Adam J. Ratner, MD, MPH, a member of the American Academy of Pediatrics (AAP) Infectious Diseases Committee, told CIDRAP News. The AAP has released an updated FAQ on congenital measles last month.
Ratner explained that most of what is known about the disease comes from individual case studies and series. For this reason, it is impossible to extrapolate how many pregnant women with measles will have a child with congenital measles.
Additionally, the case definition for congenital measles is strict: only measles infections that occur during the last two weeks of pregnancy or the first 10 days after delivery are considered congenital. But Ratner cited a 2021 case series in France describing asymptomatic infants who tested positive for measles more than 20 weeks after maternal infection.
Another series of cases conducted during the major measles outbreak in Canada in 2025, described 51 pregnant women who contracted the virus, resulting in nine cases of congenital measles. One of the nine patients died.
There is certainly underreporting of prenatal measles, as mild cases of measles during pregnancy may go undetected.
The denominator problem is compounded by reporting. “There is definitely underreporting of prenatal measles, because mild cases of measles during pregnancy may go undetected,” Ratner said.
State recommends MMR before pregnancy
In its alert, the Pennsylvania Department of Health urges women to get the measles, mumps, and rubella (MMR) vaccine before pregnancy. MMR is not recommended once pregnancy begins because it contains live viruses.
If an unvaccinated pregnant woman is exposed to measles, she has six days to undergo immunoglobulin treatments. If a pregnant woman who received the two-dose MMR series during childhood is exposed to the virus, she should be well protected against the virus.
“The presentation of congenital measles infection is highly variable, ranging from asymptomatic, to classic measles rash, to fulminant, multisystem disease and death,” the state health department said. Treatment includes supportive care and, in the case of symptomatic infants, vitamin A, unless contraindicated. Asymptomatic infants born to mothers with an active infection (appearance of a rash within 14 days of birth) may also receive immunoglobulins.
Since yesterday, Pennsylvania has confirmed 1,286 cases of measles, 109 of which were reported last week. The state dashboard lists five deaths from measles, despite a sixth death reported earlier this month in Franklin County.
In an email to CIDRAP News, the Pennsylvania Department of Health said it is still investigating the Franklin County death and that the death will not be labeled “measles-associated” until there is evidence that the death met all state criteria, including proof of measles infection and a positive laboratory test within the previous 30 days.
Gn Health
