Vaccination is the most effective strategy against measles and should be offered to nonimmune reproductive-age women before pregnancy, a narrative review of measles-related risks in pregnancy recommended inObstetrics & Gynecology.

Because vaccination during pregnancy is contraindicated and no licensed antiviral therapies exist, susceptible pregnant women should receive a single dose of intravenous immunoglobulin at 400 mg/kg within 6 days of exposure to this highly contagious infection, according to the review’s author, Naima Joseph, MD, MPH.

“Recent outbreaks of measles in the United States with decreasing vaccination rates as well as a higher proportion of measles in reproductive-age people suggests increased potential for measles in pregnancy,” Joseph, an assistant professor in the Division of Maternal Fetal Medicine at Boston University School of Medicine in Boston, told Medscape Medical News.

In this year’s US outbreak, “33% of confirmed cases have occurred in individuals age 20 years and older, and this shift increases the likelihood that obstetricians will encounter measles in clinical practice.”

According to the CDC, there were 1723 confirmed cases of measles in the US as of November 12 — including 573 cases in people in the reproductive age group of 20 years or older.

Pregnancy-related immunologic changes increase maternal vulnerability to respiratory infections such as measles, increasing disease severity.

Measles during pregnancy is associated with poor maternal and fetal outcomes, Joseph said. “There’s an increased risk of pneumonia and the need for respiratory support, and some studies suggest an increased risk of maternal death.”

The fetal and neonatal risks include a higher chance of stillbirth and prematurity, as well as an increased risk for measles transmission to the newborn, she added.

“Newborn measles, also called congenital measles, is associated with higher risk of severe measles. Although perinatal transmission is rare, congenital measles is linked to higher infant mortality.”

“There’s been a case of measles during pregnancy in the recent outbreak in Texas, and similar cases in Ontario, Canada,” Kevin A. Ault, MD, a professor of OB/GYN at Western Michigan Homer Stryker MD School of Medicine in Kalamazoo, Michigan, told Medscape Medical News.

He noted that several maternal deaths occurred during the measles outbreak of 1990.

Ault, who was not involved in the review, is also vice president of the National Foundation for Infectious Diseases and a member of ACOG’s Immunization, Infectious Disease, and Public Health Preparedness Expert Work Group.

Both the measles, mumps, and rubella (MMR) and MMR-varicella vaccines are contraindicated in pregnancy because of the theoretical risk for fetal congenital rubella syndrome, Joseph noted. The CDC has estimated the theoretical risk for this syndrome after vaccination with the rubella vaccine to be just 0%-1.6%, and only one case has been reported. Breastfeeding is not a contraindication to vaccination and may confer protection in infants up to age 3 months.

“Vaccination history is the most important part of determining immunity to measles,” said Ault. “Everyone considering pregnancy should have received the routine childhood doses of the MMR vaccine.” That is usually two doses after turning 1 year old. “If you missed those doses, you can be vaccinated as an adult,” he said.

Women should wait 30 days before trying to conceive a pregnancy after the MMR vaccine because of the theoretical risk for congenital infection.

The MMR vaccine is more than 50 years old, he said, and there is reassuring data about the safety and effectiveness in both children and adults. “With the current outbreaks in the USA and Canada, there really isn’t a plan B.”

According to Joseph, a concerted effort by physicians and nurses is needed to ensure all women of reproductive age have immune protection. “Clinicians should refer to guidelines determining measles vaccination eligibility, assess for vaccine eligibility in their patients, and provide vaccination.” Clinicians should remind their patients that measles vaccines are safe and highly effective in reducing measles infection and subsequent complications, she said.

Joseph indicated no specific funding for this review but reported receiving funding support from the Agency for Healthcare Research and Quality, the CDC, and Pfizer, as well as royalties from UpToDate. Ault had no conflicts of interest to disclose.