Retrospective diagnosis of congenital rubella.

One hundred and five children and adolescents with impaired hearing and 19 with impaired vision underwent in vitro tests (lymphocyte responsiveness and serum antibody to rubella) for retrospective diagnosis of intrauterine rubella. Tests yielded results consistent with intrauterine rubella in 30 (29%) of the patients with impaired hearing but only one (5%) of those with impaired vision. In addition, the reported incidence (10.8%) of rubella as a cause of deafness was obtained by questioning parents before the tests. Of 27 patients with impaired hearing of unknown aetiology but reported rubella contact during the pregnancy, seven (26%) had test results consistent with intrauterine rubella. The incidence of intrauterine rubella as a cause of deafness is probably underestimated when the diagnosis is based on the presence of several classic features.