Rubella in pregnant Danish women 1975-1984

During the period 1975 to 1984, 1,346 pregnant women had the diagnosis of rubella serologically confirmed. The incidence was one per 530 pregnancies. Of 1,330 women, 623 were subjected to therapeutic abortion. Thirty-five aborted spontaneously and 672 continued pregnancy; among these, four infants were stillborn. In 111 of 520 infants, rubella specific IgM was found in blood drawn from the umbilical cord. The frequency of rubella specific IgM in infants after maternal rubella during the first trimester was 50 percent (7 of 14); in the second trimester, the frequency had been reduced to 14 percent in the 28th week of pregnancy; and in the third trimester, the frequency rose again to 28 percent. Malformation occurred only in infants whose mothers had been infected before the 12th week. Preconceptional rubella was found in 32 cases; seven of these women carried their pregnancies to successful termination. In none of the infants was rubella specific IgM found, and no abnormalities could be found at birth. The importance of immunisation of women in the fertile age group is emphasised. By testing a blood sample from the fetus for rubella specific IgM, it is possible to show prenatally if a fetus has congenital rubella. This method will probably allow reduction of the number of therapeutic abortions after maternal infection between the 12th and the 16th week of pregnancy.