Significance of raised immunoglobulin M levels in cord blood of small-for-gestational-age infants.

Cord IgM values were determined in small-for-gestational-age infants born at Hammersmith Hospital during a 5 1/2-year period. 121 (12.5%) infants had levels more than 0.2 g/l; in 92 these were between 0.21 and 0.3 g/l. In only 18 (14.8%) was a level of 0.4 g/l exceeded, and 5 proved cases of intrauterine infection--rubella (2), syphilis (2), and toxoplasmosis (1)--were in this group. The factor most often associated with cord IgM more than 0.4 g/l was prolonged rupture of the membranes. There was an increased incidence of blood group B among the mothers, probably reflecting the greater number of nonCaucasian women giving birth to small-for-gestational-age infants. Determination of cord IgM did not help significantly indiagnosis.