Nellnell has summed most of them up.
Antibodies are usually done with your blood group as if you test positive to certain antibodies it can put your bub at risk of certain things like jaundice, been anemic etc.
Bloodgroup mainly to see if your negative and you need anti-D.
They do your STDS so VDRL, HepB,C, HIV sometimes clymidia as if you have something it again can put bub at risk (Clymidia can cause problems with eye sign, VDRL infection of the brain, then Hep you want to know as bub usually has a bath soon after birth to reduce the risk it might be transmitted afterbirth although I believe this is very very low)
There the main ones.