IgG subclass concentrations in preterm neonates

Serum IgG subclass concentrations were measured in 158 sera from preterm, appropriate for gestational age, infants born between 27 and 37 weeks of gestation, pregnancy, delivery and neonatal period being uncomplicated in all cases. At birth the IgG subclass concentrations were inversely correlated to the degree of prematurity. The IgG subclass concentrations decreased mainly proportionately during the neonatal period. The most immature infants born before the 30th week of gestation had critically low concentrations of all IgG subclasses. All immature infants, already in the first week after birth, showed capacity for IgG1 and IgG3 synthesis.