Babies Are Catching Measles in Utero for the First Time in Decades

Pennsylvania’s measles outbreak has reached pregnant women and newborns, with congenital infections reported in the state for the first time in decades. At least 1,398 people have been infected this year, though officials expect the true total to be higher; Amish communities with low vaccination rates have been especially affected. Many cases are among adults ages 18 to 49, who grew up when measles was uncommon and may lack immunity. Infection during pregnancy can cause miscarriage, premature labor, or low birth weight, and historical estimates suggest roughly one in four babies born to mothers sick near delivery may contract measles. The scale of congenital infection is difficult to establish because there is no national definition or systematic tracking, and the usual diagnosis may miss mild cases.

Doctors have little evidence to guide care because congenital measles has been rare. Measles can erase immune memory and, in rare cases, lead years later to a usually fatal brain disease; that complication may develop sooner or more often in babies infected before birth. Pediatric specialists have issued treatment guidance based partly on experience with older children and recent Canadian cases. Pennsylvania physicians are recommending vitamin A and antibodies, while acknowledging that evidence is limited and that the outbreak may provide data to improve care. Preventing infection in pregnant women is central, but they cannot receive the measles vaccine during pregnancy. A Lancaster County midwife argues she should be allowed to vaccinate household members to protect expectant mothers; opponents question whether traditionally trained midwives have sufficient medical training, even as they recognize their close ties to families wary of formal health care.