At my 28 week appointment?

i had a blood test for my haemoglobin and antibodies, what antibodies are they looking for are they looking for hepatitus, hiv and all the scary ones again? i had these done at my 12 week scan. i just want to no what exactley they will find and what they are looking for. dont they have to have my consent if they are screening for things like hiv? my 1st blood test was negative for that by the way touch wood i never have or get it but i am really confused and dont no what to expect if they find any antibodies as i dont no what they are looking for? i am 28 weeks pregnant.