Distribution of IgG subtypes in maternal anti-D sera and their prognostic value in Rh haemolytic disease of the new-born.

In 107 Rh(D)-immunized women having Rh(D)-positive pregnancy screening for IgG subtypes was carried out between the 34th and 36th week of gestation. Using polyclonal IgG subtype-specific reagents, all four IgG subclasses were detected in anti-D sera though IgG1 and IgG3 were the most predominant classes. IgG3 anti-D was usually low titre. At the same level of Rh(D) antibody titre, haemolytic disease of the new-born was more severe when anti-D was IgG1 type than IgG3 type. When the IgG1 and IgG3 anti-D subtypes existed together, the risk of having a stillborn child was very high compared to other subtypes (IgG1 + IgG3 34.8%, IgG1 19.2% and IgG3 15.4%).