Congenital rubella infection: escape of one monozygotic twin with two amnions, one chorion, and single placenta.

We report a 2 amnions, 1 chorion, single placenta, monozygotic identical twins, who were born by a mother with a subclinical rubella infection during the gestation; one twin had a congenital rubella infection, the other escaped from it. Both twins were premature and small for their gestational age at birth. They both had an intraventricular hemorrhage ascribed to prematurity. One had a strong positive rubella IgM antibody for more than 3 months and a persistent IgG antibody for more than 1 year. The other had a fading rubella IgG antibody within 3 months, and a negative IgM. The baby with the congenital infection of rubella did not have a defective appearance, but the auditory brain stem evoked potential test showed abnormal findings. In monozygotic identical twins, vessel communication usually exist and the escape of a twin from rubella is a rare condition; there have been only two such events reported in the English literature.