Symptoms generally appear between 4 and 14 days after exposure. About 20 percent of infected people have no symptoms and about 50 percent of adults have had the infection in childhood, often without knowing it. There is no vaccine against fifth disease. Fortunately, most fetuses are unaffected when their mothers contract the virus. Fifth disease in pregnancy has not been proven to cause birth defects.
Any susceptible person can catch fifth disease.
It's best for a pregnant woman to be cautious and assume she is susceptible, especially if she is among the most likely to be exposed, i.e., women with young children, and those who work as teachers and childcare providers. A large Danish study recently reported that, during a fifth disease outbreak, about 13 percent of susceptible pregnant women caught the virus. Susceptible nursery school teachers and others who worked with young children were three times more likely to become infected than women who worked in other professions. However, most susceptible pregnant women caught the virus from their own children. The more children a susceptible pregnant woman had at home, the more likely she was to become infected.