Pennsylvania's Measles Outbreak Is Now Threatening Newborns in the Womb

A Rare Danger Returns

Pennsylvania health officials have confirmed that congenital measles — a measles infection in a newborn contracted from the mother — has been identified "for the first time in decades." The announcement is a stark signal of just how far the country's measles crisis has escalated, and it carries serious implications not just for Pennsylvania, but for every state where vaccination rates have been quietly slipping.

The Pennsylvania Department of Health issued an alert on Monday to doctors about an increase in measles infections in pregnant women, as well as a concerning rise in congenital measles — a disease that's rarely, if ever, seen in the U.S. Now that dozens of pregnant Pennsylvania women have contracted measles in the state's ongoing outbreak, the potentially fatal infection passed from mother to baby in utero is poised to pose clinical challenges for physicians facing a disease they've never seen in practice.

The Scope of the Outbreak

The department said that 66 pregnant women in Pennsylvania had been diagnosed with measles since the state's outbreak began in April. At least six babies in the state have been born with measles. Of the six deaths reported in the state, at least two have been in infants, but it's not known if they had congenital infections.

As of this week, there have been 4,410 measles cases in the U.S. this year. In Pennsylvania alone, there have been 1,286 cases. True numbers may also be obscured, as the outbreak has largely been limited to Amish families who don't always seek conventional medical assistance. Experts warn that the real toll is almost certainly higher than official figures suggest.

Why Congenital Measles Is So Dangerous

Getting measles while pregnant increases the risk of miscarriage, early labor, and low birth weight. But the risks don't stop at birth. The state noted that newborns who contract the virus before birth are at risk of developing subacute sclerosing panencephalitis, a rare and potentially fatal inflammation of the brain that can emerge years after the initial infection.

According to the American Academy of Pediatrics, an estimated 25 to 30 percent of babies with mothers who have a measles infection at birth are also infected. Only measles infections that occur in the last two weeks of pregnancy or the first 10 days post-delivery are considered congenital. Few pediatricians have ever treated a newborn with congenital measles, presenting a real clinical challenge for physicians. In response, the American Academy of Pediatrics added a "frequently asked questions" page about congenital measles to its website in September.

Prevention and What Comes Next

In its guidance, the Pennsylvania Department of Health advised that "getting vaccinated BEFORE pregnancy is the best way to prevent measles and congenital measles." The MMR vaccine is not recommended once pregnancy begins because it is a live virus vaccine. However, non-immune pregnant women and babies who are exposed to measles have a six-day window where they can be given immunoglobulin, which can provide protection against measles infection or reduce the risk of serious illness.

Congenital measles was uncommon in the U.S. before the measles vaccine was introduced in the early 1960s because most women had been infected as children. But as vaccination rates plummet and measles outbreaks become more common, the risk of congenital measles is growing. Pennsylvania's crisis is a window into what happens when herd immunity erodes — and a warning to the rest of the country that diseases once considered conquered can return, and when they do, the most vulnerable pay the highest price.