a disease that is caused by the rubella virus and that produces symptoms similar to measles, although it is less contagious. A woman who develops German measles during pregnancy has a 25% chance of giving birth to a child with congenital rubella. The rate of malformation in the fetus ranges from a low of 6% if the virus is contracted during the 3rd month of pregnancy to as high as 50% in the 1st month. The birth defects include malformations of the eyes, ears, and central nervous system (see congenital rubella syndrome). Also called rubella.