Placental transport efficiency is relatively higher at lower maternal levels.

<p>In general, IgG1 is transported better than IgG4, both of which are transported better than IgG2 and IgG3, which have similar transport rates. Two-tailed Pearson correlation revealed a significant correlation for all subclasses, IgG1 R² = 0.379, P = 0.0018; IgG2 R² = 0.2910, P = 0.0096; IgG3 R² = 0.2415, P = 0.0202; IgG4 R² = 0.2881, P = 0.0121. Thus, for all subclasses, relatively more IgG was transported at lower maternal IgG.