RESUMEN
In a prospective study, serum IgG, IgA, IgM, and IgG subclass levels of 66 preterm infants (gestational age less than or equal to 34 weeks) were measured sequentially from birth to 12 months of life. Infants were divided into two groups, comparable for gestational age, birth weight, sex, and intensive care, on the basis of admission order: the treatment group, consisting of 33 infants who received intravenous immune globulin therapy (0.5 gm/kg at 10-day intervals) prophylactically, and the control group, consisting of 33 infants who did not receive. Twenty of the 33 treated infants received only one infusion and the remaining 13 received two to five infusions. The mean number of infusions per neonate was 1.96. Immunoglobulin measurements showed that the proportion of infants with an IgG level of greater than or equal to 7 gm/L on the tenth and thirtieth days of life was significantly higher in the treatment than in the control group (p less than 0.01). At the same ages, mean serum IgG, IgG1, and IgG2 concentrations were significantly higher in the treatment group (p less than 0.001). Thereafter levels in both groups fell progressively, reaching their lowest point between 3 and 5 months of age. During this period, profound hypogammaglobulinemia (IgG less than 2 gm/L) was observed in 3 of 33 treated and 11 of 33 untreated infants (p less than 0.05). By 3 months of age, mean serum total IgG concentrations were still significantly higher in treated than in untreated infants (p less than 0.05), but the IgG subclass concentrations were not. After the third month, no significant differences between the two groups were observed. Moreover, the sequentially measured serum IgA and IgM levels in the two groups remained comparable from birth to age 12 months. The IgG level at different ages from 3 to 12 months was not correlated with either birth weight or the number of infusions performed during the neonatal period (p greater than 0.1). We conclude that prophylactic intravenous administration of immune globulin to preterm infants with a birth weight of 1000 to 2000 gm, at a dose of 0.5 gm/kg every 10 days, results in maintenance of a satisfactory serum IgG level throughout the high-risk period for infections. Such treatment does not have a suppressive effect on subsequent serum immunoglobulin concentrations.