There have been at least 1,375 confirmed cases of measles in the U.S. in 2025, 27 of which are in Colorado. Most cases (92%) are individuals with no documented immunizations or who are known to be unvaccinated. Measles is often introduced into communities by unvaccinated travelers who become infected during international travel. The virus is highly infectious; one infected person can spread it to as many as 18 others. It can also live on surfaces for up to two hours, meaning people in the same space hours later may also be exposed.

In May 2025, a flight from Istanbul to Denver was linked to at least seven measles cases and resulted in the exposure of a large number of travelers both on that flight and within Denver International Airport. In response, on May 28, 2025, the Centers for Disease Control and Prevention updated its guidelines, recommending that all international travelers be fully vaccinated against measles with two doses.

Vaccination against measles is highly effective and recommended. However, the MMR vaccine (measles, mumps and rubella) is not recommended during pregnancy.

Why Measles Is a Concern During Pregnancy

Some individuals, including unvaccinated and pregnant persons, children younger than 5 years old and severely immunocompromised people, are at increased risk of severe illness and complications of measles. In pregnancy, this means a higher risk of pneumonia, the need for oxygen support or mechanical ventilation, and hospitalization. This is similar to the increased risks pregnant people face with COVID-19 infection compared with others in the community.

There are also fetal and newborn risks with measles infection during pregnancy, including miscarriage, stillbirth and premature birth. For infected infants, there is an increased risk of death from measles infection. There are no birth defects associated with measles infection during pregnancy.

Many people ask about birth defects and measles. It can be confusing because of the similar names of related diseases. Measles can also be referred to as rubeola. Rubella, sometimes called German measles, is different. Rubella is linked to specific birth defects, including cataracts and hearing loss.

Can You Get the MMR Vaccine During Pregnancy?

Measles is almost entirely preventable through vaccination. One dose is about 93% effective, and two doses are about 97% effective in preventing later measles infection.

You are presumed immune to measles if any of the following are true:

• You have documentation of two measles vaccine doses as a child or one dose as an adult
• You were born before 1957
• You had confirmed measles as a child
• A blood test shows immunity (positive measles IgG test)

If a person has presumed immunity, no additional boosters are necessary, though there is no harm in receiving additional doses. However, pregnancy is a contraindication for the MMR vaccine because it is a live virus vaccine. This recommendation is made out of caution. There are no known adverse maternal or fetal effects if the vaccine is given inadvertently during pregnancy, such as before someone knows they are expecting. The MMR vaccine is safe to receive while breastfeeding.

What to Do if You’re Not Immune or Vaccinated

If you are not clearly immune, an additional MMR booster can be given — but only after delivery. Pregnant people and young children have additional protection when everyone around them — family members, caregivers and others — is fully vaccinated.

Blood testing to determine immunity is not routinely recommended. A positive result is highly accurate, but a negative result does not always mean someone is susceptible.

If you are nonimmune or unvaccinated, take extra precautions in public places, especially when traveling:

• Wash hands regularly with soap and water
• Cover your mouth and nose when sneezing
• Limit contact with individuals who are sick or may have been exposed

If you think you have been exposed, contact your health care provider as soon as possible. Depending on the situation, people who cannot receive an MMR booster — including pregnant individuals and infants younger than 6 months — may be candidates for post-exposure prophylaxis medication.

The Bottom Line

Media reports about measles can be frightening, but most of the population is well protected through vaccination. About 91% of the U.S. population has received measles immunization.

Before pregnancy, or between pregnancies, is a good time to optimize your health, including staying up to date on vaccinations and preventive care.

If you have questions about measles, infectious diseases or vaccines, talk with your care team or visit our find a provider page. Visit the Colorado Department of Public Health page on measles for the latest information. 

About Dr. Anna Euser

Dr. Euser is a Colorado native who earned her MD and PhD at the University of Vermont. She completed her obstetrics and gynecology residency at the University of Minnesota before returning to Colorado in 2013 for a maternal-fetal medicine fellowship at the University of Colorado.

Currently, Dr. Euser is an associate professor of maternal-fetal medicine at the University of Colorado, where she provides comprehensive care for patients with complicated pregnancies. She manages complex maternal medical conditions during pregnancy, has expertise in ultrasound for fetal conditions, and performs prenatal diagnostic procedures such as chorionic villus sampling and amniocentesis. She also works with medical students, residents and fellows in labor and delivery.

Dr. Euser has a special interest in the effects of high-altitude living on pregnancy and in improving the use of ultrasound in low-resource settings. She is active in several research projects in these areas.

In 2024, Dr. Euser was honored as the American College of Obstetricians and Gynecologists (ACOG) Immunization Champion, recognizing her leadership and commitment to advancing maternal immunization and public health.

She sees patients at multiple clinic sites along the Colorado Front Range.