Congenital rubella syndrome: The constellation of abnormalities caused by infection with the rubella (German measles) virus before birth. The syndrome is characterized by multiple congenital malformations (birth defects) and mental retardation.

The individual features of the syndrome include growth retardation, microcephaly (abnormally small head), cataracts, glaucoma, microphthalmia (abnormally small eyes), cardiovascular malformations, hearing loss, and mental retardation. Deafness is common. After birth the child may develop diabetes due to gradual destruction of the pancreas by the rubella virus.

The child has a 50% risk of being born with the congenital rubella syndrome, if the mother is infected with rubella in the first trimester (the first third) of pregnancy. Risks still exist with infection in the second trimester

The discovery of the congenital rubella syndrome by the Australian ophthalmologist (eye doctor) NM Gregg in 1941 is of historic importance. It provided the first evidence that the placental barrier between the mother and the fetus does not fully protect the fetus from teratogens (agents that can cause birth defects).

The rubella epidemic of 1963-1965 resulted in 1,800,000 infected individuals, approximately 20,000 fetal deaths and about 30,000 infants born with congenital rubella syndrome. Since the introduction of the rubella vaccine in 1969 there are less than 120 cases of congenital rubella syndrome reported each year.

The condition also goes by the name of fetal rubella effects.