A toxoplasmosis test is a blood test that checks for antibodies to the Toxoplasma gondii parasite. Your body's natural defense system (immune system) will make these antibodies only if you have been infected by this tiny parasite. A toxoplasmosis test is done to check if a: Pregnant woman has antibodies from a toxoplasmosis infection. If she has the IgG type of antibody, that means an infection occurred in the past and the baby does not have a chance of becoming infected. If she has the IgM type of antibody, that means the infection is recent and the baby does have a chance of becoming infected. Baby has toxoplasmosis. Person with a weakened immune system, such as someone who has HIV, has a chance of getting a toxoplasmosis infection.