Measles, mumps, and rubella are viral diseases that may adversely affect nonimmune pregnant women and their fetuses/neonates. Prevention of these diseases and their complications can be achieved through measles-mumps-rubella (MMR) vaccination before pregnancy. The vaccine is contraindicated during pregnancy, because it contains live, attenuated viruses that pose a theoretical risk to the fetus. However, accidental receipt of MMR vaccination is not known to cause maternal/fetal complications. MMR immunization is recommended to nonimmune obstetric patients upon completion or termination of pregnancy.