Transplacental passage of intravenous immunoglobulin in the last trimester of pregnancy.

Immunoglobulin G was given intravenously (IVIgG) to pregnant women (27 to 36 weeks gestation) with signs of chorioamnionitis who were at risk for preterm delivery. Twenty-four patients received antibiotics alone (control group). Twenty-seven patients received the same antibiotics in combination with IVIgG, either 12 gm in 12 hours (low IVIgG dosage) or 24 gm on each of 5 consecutive days (high IVIgG dosage). Transplacental passage of IVIgG was shown to be a function of gestational age and of dose. Up to the thirty-second week of gestation, IgG infusions had no effect on IgG concentrations in cord sera. After that time, cord serum IgG levels were significantly higher in the high-dose group compared with the low-dose and control groups. All four subclasses of IgG, and two different antibodies present in the IVIgG preparation passed from the mother to the fetus. Thus the infused IgG mimicked the transplacental passage of endogenous IgG.