Why Rh conflict happen but no ABO conflicts? I wonder why Rhesus conflict can happen during pregnancy and mother can make antibodies against Rh protein (I think the correct name is D protein), but it doesn't happen if mother has different ABO type than the child?

It happens, but it is very rare.

**Anti-A** and **Anti-B** antibodies are IgM type. They **do no cross the placenta**. Sometimes IgG can be produced and lead to the hemolytic disease of the newborn.

**Anti-D** antibodies are IgG type and **can pass through the placenta**.