The worst measles outbreak in the United States since 1992 has experts concerned about preventing the infection in pregnant and reproductive-aged women. As of June 13, 1044 individual cases of measles have been confirmed in 28 states, and that number is expected to rise.
Pregnant women who develop measles have an increased risk for severe complications, including hospitalization and pneumonia. Having measles during pregnancy also endangers the fetus; risks include miscarriage, stillbirth, low birth weight, and preterm delivery. Infants born of mothers who have an active measles infection are at increased risk for congenital measles.
Unvaccinated and undervaccinated pregnant women and infants aged 12 months or younger are among those with a higher likelihood of having severe illness and complications if they get measles.
In response to the ongoing outbreak, Alisa Kachikis, MD, from the University of Washington, Seattle, and colleagues published a revised consensus statement with guidance for clinicians caring for pregnant and reproductive-aged women who are at high risk of developing measles. The American College of Obstetricians and Gynecologists (ACOG) supports the consensus statement and has released a practice advisory in collaboration with the University of Washington.
Both documents emphasize the importance of receiving two doses of the measles-mumps-rubella (MMR) vaccine, which is safe and is 97% effective against measles. Despite the vaccine‘s high rate of efficacy, approximately 92% to 95% of those in a community must be immune to measles to prevent ongoing transmission, and vaccination rates have dropped below that level in recent years.
“These measles outbreaks have been linked to travelers bringing back cases of measles from other countries. This situation combined with low vaccination coverage among certain communities in the United States leads to pockets of vulnerable communities and contributes to outbreaks such as the one we are currently experiencing,” according to the practice advisory.
The consensus statement includes algorithms for managing high-risk pregnant patients, such as women living in or traveling to areas experiencing an active outbreak.
The consensus statement authors, the ACOG, and the Centers for Disease Control and Prevention (CDC) have provided the following recommendations for those caring for pregnant and reproductive-aged women.
Reproductive-aged women and those considering pregnancy should determine their measles immune status with their primary healthcare provider before becoming pregnant and should receive the MMR vaccine if they are not immune.
“After receiving the MMR vaccine, women should wait 4 weeks prior to attempting pregnancy given theoretical risks to the fetus with live vaccines; however, inadvertent MMR vaccination in the periconception period or in early pregnancy should not be considered an indication for termination of pregnancy,” the practice advisory authors explain.
For low-risk individuals, including pregnant women, one documented MMR dose is sufficient. For those with a high risk for measles, a documented history of two prior MMR vaccine doses is required to confirm immunity. Obstetrician-gynecologists should consult their local health departments for assistance in determining the number of vaccine doses necessary.
In areas experiencing ongoing outbreaks where sustained transmission is occurring in close-knit communities, clinicians may consider serologic testing for measles IgG in pregnant women who have no documented measles immunity.
Pregnant women who are suspected of having been exposed to measles and who are not immune should receive intravenous immunoglobulin (IGIV) treatment within 6 days of exposure to measles. Pregnant women who have been exposed and for whom there is no evidence of immunity and serologic testing is not promptly available should also receive IGIV.
Most women are immune to measles as a result of prior MMR vaccination; however, because measles can be risky for pregnant women, clinicians should carefully and promptly investigate possible infection or measles exposure. Physicians should follow guidance from their local health department regarding testing.
Post partum, women for whom there is no evidence of immunity to measles should receive the MMR vaccine.
Talking With Patients About Vaccination
The authors caution about parents opting out of vaccinating their children, saying doing so “allows population immunity to drop below the threshold levels needed to stop outbreaks of measles, placing vulnerable patients such as pregnant women, infants under 12 months of age, and immunocompromised individuals at increased risk.”
At prenatal visits, clinicians should discuss the importance of vaccination, particularly for measles, with parents and urge them to vaccinate their children. Most women begin deciding about vaccinations for their children before or during pregnancy; therefore, having conversations about vaccines is particularly important for first-time parents who may be more hesitant about vaccines.
The ACOG will continue to provide updates as available while these measles outbreaks continue. Additional information is available on the CDC’s Measles Cases and Outbreaks webpage. The University of Washington’s obstetric consensus statement, which is supported by the ACOG, is also available online.