The influence of prematurity and low birthweight on transplacental antibody transfer in Sri Lanka.

The influence of gestational age, the neonate's birthweight, and maternal age, weight, height and parity on transplacental antibody transfer was assessed in 141 mothers from Sri Lanka and their neonates. Paired blood samples were collected from the mothers and the umbilical cords of the newborns. The sera separated from these samples were categorized as: preterm but adequate birthweight (< 37 weeks' gestation and birthweight > or = 2500 g); term but low birthweight (> or = 37 weeks' gestation and birthweight < 2500 g); or term and adequate birthweight (> or = 37 weeks' gestation and birthweight > or = 2500 g). Neonatal and maternal sera were assessed, in ELISA, for specific IgG antibodies against measles virus (MeV), herpes simplex virus type-1 (HSV1), respiratory syncytial virus (RSV), varicella-zoster virus (VZV), tetanus toxoid (TT), diphtheria toxoid (DT), and Streptococcus pneumoniae (Pn) and Haemophilus influenzae type-b (Hib) capsular antigens. Placental antibody transfer to certain antibody specificities was significantly lower in preterm neonates than term neonates. Thus the ratios between geometric mean cord antibody levels and geometric mean maternal antibody levels (the antibody-transfer ratios) were lower in preterm sera than term sera, for MeV (1.51 v. 2.03; P = 0.03), HSV1 (1.29 v. 1.76; P = 0.04), VZV (0.96 v. 2.50; P = 0.01), TT (1.13 v. 1.33; P = 0.04), DT (1.03 v. 2.39; P = 0.02), Pn (0.68 v. 0.98; P = 0.01) and Hib (0.58 v. 0.98; P = 0.00). Geometric mean levels of antibody to MeV, VZV, TT, DT and Pn were also significantly lower in preterm neonates than term. Compared with the values for 'adequate-birthweight' sera, low birthweight was independently associated with significantly lower levels of antibody transfer, for MeV (with antibody-transfer ratios of 1.51 v. 2.03; P = 0.02), VZV (0.99 v. 2.50; P = 0.03), TT (1.01 v. 1.33; P = 0.04) and DT (1.16 v. 2.39; P = 0.04) and significantly lower levels of antibodies to MeV, HSV1, VZV, TT, DT and Pn in the neonates. Maternal age, weight, height and parity had no independent influence on placental IgG transfer for antibodies to any of the pathogens investigated. These results demonstrate that prematurity and low birthweight may influence the level of maternally acquired immunity in Sri Lankan neonates.