• Serum IgG subclasses;
  • placenta;
  • umbilical cord;

PROBLEM: We determined the maternal-fetal transport of immunoglobulin G (IgG) during the third trimester of human pregnancy.

METHOD: The concentration of IgG and its subclasses (IgG1–4) was determined in sera of blood samples from 38 pregnancies collected at the time of delivery from a peripheral maternal vein (MV) and from the placental umbilical artery (UA) and vein (UV). Gestational age varied between 28 and 42 weeks (WG).

RESULT: Whereas placental weight showed a significant correlation with gestational age, the maternal level of IgG and the ratio of its subclasses did not vary with gestational age. At 28–33 WG (n = 15) the mean values in the UA (5.91 ± 1.53 g/1) and UV (6.41 ± 1.57 g/1) for total IgG concentration were lower than in the MV (10.74 ± 2.55 g/1). At the end of gestation (37–42 WG, n = 12), IgG in both UA (11.21 ± 1.95 g/1) and UV (12.26 ± 2.06 g/1) exceeded the maternal concentration (9.69 ± 1.84 g/1). In addition to the significant positive correlation between IgG concentration in the fetal circulation (UV + UA) and gestational age (28–42 WG), an increase in the positive difference between UV and UA at the end of pregnancy indicates that there is a substantial rise in placental IgG transport capacity.

CONCLUSION: All four subclasses IgG1–4 were detectable in the umbilical circulation (28–42 WG). Whereas IgG3 and IgG4 in UA and UV had a similar concentration as in MV and remained unchanged, IgG2 increased with gestation from 0.67/0.74 g/1 (UA/UV, 28–33 WG) to 1.29/1.58 g/1 (UA/UV, 37–42 WG), but nevertheless remained lower than the level found in the MV (2.65 ± 1.12 g/1). The main increase in IgG concentration, however, was due to the substantial rise in the transport of IgG1, which increased from 4.37 ± 1.24 (UA) and 4.94 ± 1.52 g/1 (UV) at 28–33 WG to 8.94 ± 1.66 (UA) and 10.89 ± 1.96 g/1 (UV) at the end of gestation, which was even higher than the overall IgG concentration in MV.