Postnatal IgG Levels in Very-low-birth-weight Infants

We studied the gammaglobulin levels (IgG) postnatally, serially, in 42 infants of very low birthweight (mean ± SD 971 ± 225 g) with gestational ages ranging from 23 to 31 weeks. Eighteen infants (42.8%) had IgG levels of less than 100 mg/dl by a mean postnatal age of 71.2 ±16 days. The lowest level was 22 mg/dl in an infant whose birthweight was 700 g. Sixteen of the 42 infants (mean birthweight 946.8 ± 260 g) also had cord blood IgG levels determined. The mean cord blood IgG was 413.5 ± 163 mg/dl. This had dropped to 140.3 ± 87 mg/dl by 57 days, a drop of 66 percent. As expected, the lowest IgG levels postnatally was a reflection of the degree of prematurity and the length of postnatal age. Such extremely low levels of IgG have not been reported previously.