Adult immunization rates have fallen short of national goals partly because of misconceptions about the safety and benefits of current vaccines. The danger of these misconceptions is magnified during pregnancy, when concerned physicians are hesitant to administer vaccines and patients are reluctant to accept them. Routine vaccines that generally are safe to administer during pregnancy include diphtheria, tetanus, influenza, and hepatitis B. Other vaccines, such as meningococcal and rabies, may be considered. Vaccines that are contraindicated, because of the theoretic risk of fetal transmission, include measles, mumps, and rubella; varicella; and bacille Calmette-Guerin. A number of other vaccines have not yet been adequately studied; therefore, theoretic risks of vaccination must be weighed against the risks of the disease to mother and fetus. Inadvertent administration of any of these vaccinations, however, is not considered an indication for termination of the pregnancy.