Microcephaly and congenital cytomegalovirus infection: a combined prospective and retrospective study of a Swedish infant population.

Microcephaly and its etiology were studied in an unselected Swedish urban infant population. Virtually, all live-born infants (14,724) born between October 1977 and December 1983 in the city of Malmö, Sweden, were included in the study. Special attention was given to the role of congenital infections, particularly to cytomegalovirus infection. The infant population was studied from two points of view. One part of the study was prospective and based on regular cytomegalovirus isolation in urine within the first week of life. About 80% of the newborns were adequately studied by this test. None of 56 infants shown to be cytomegalovirus excreters (congenitally infected) and followed up were born with or developed microcephaly (head circumference smaller than 3 SD below the mean for age and sex) during the first 1 to 7 years of life. However, two of the 56 infants had a head circumference of -2 SD. In the beginning of 1985, an inventory was made of the presence of symptomatic microcephaly in the above mentioned population still living in the city or deceased there. Of about 10,000 such children, 12 were found to have symptomatic microcephaly. By studies of personal, clinical, and laboratory data and by retrospective serologic studies of frozen pre- and postconceptional maternal sera, a possible explanation or a recognized syndrome was obtained in ten of the 12 cases. In one of them, the mother had a primary cytomegalovirus infection, possibly in early pregnancy. Although the infant had symptoms compatible with a congenital infection, no laboratory evidence of transmitted infection was found. In no case were congenital rubella virus or Toxoplasma gondii infections suspected.