All of the folowing are known causes of recurrent abortion except:
As discussed in previous question TORCH infection do not lead to recurrent abortion.
SLE is an established cause for recurrent abortion
SLE is associated with antiphospholipid syndrome (anti-cardiolipin antibodies) and is known to cause recurrent abortions.
RH incompatibility is a known cause for spontaneous abortion and may lead to recurrent abortions if it remains unrecognized. Syphillis also does not lead to recurrent abortions but if you have to rule out one option between TORCH infection and syphillis go for TORCH infection.
TORCH infections
SLE
Rh incompatibility
Syphilis