If a woman has rubella during pregnancy, the rubella virus can induce many different birth defects (known as 'Rubella Syndrome' or 'Congenital Rubella'), some of which are quite severe.

Among the defects doctors have seen in congenital rubella are eye defects (cataracts, glaucoma, "microphthalmia" ), heart problems (defects of the wall between the two sides of the heart, narrowing of the arteries to the lungs, and an open duct bypassing the lungs), ear problems (deafness caused by defects in the nerves and sound-sensing organs), and neurologic problems (including mental retardation) — among others.

For that reason, obstetricians test every pregnant woman to make sure that she is immune to rubella, children are usually immunized with the MMR vaccine against the virus. A single dose of the vaccine usually gives lifelong protection. This helps protect non-immune pregnant women too, by reducing the chance of their being exposed to rubella by sick children.