Congenital toxoplasmosis is a fetal infection following the transplacental transmission of Toxoplasma gondii in a mother who seroconverted during pregnancy. Neonatal diagnosis has recently been improved through the identification by L’Ollivier et al. and Peyclit et al. of a congenital toxoplasmosis pathognomonic marker: the IgM triplet, corresponding to three bands of high molecular weight of 75, 90 and 100 kDa respectively found on the immunoblot pair profile mother-child. This is a new concept, as these three IgM bands do reflect an immunological response against proteins involved in mother-to-child transmission of Toxoplasma gondii. These proteins could be Toxoplasma gondii secreted effectors or not playing a role in the processes of invasion, modulation of the host cell immune system as well as in parasitic virulence. In this study, immunoproteomic techniques allowed us to identify 32 interesting protein spots on immunoblot, including 4 interesting spots specific to the IgM triplet. After protein identification of these spots by LC-MS/MS technique, we showed here that several Toxoplasma gondii proteins were good candidates for the IgM triplet. It turns out that each of these proteins is, directly or indirectly, involved in the process of cellular invasion and therefore probably in the process of transplacental invasion of Toxoplasma gondii. The identification of these proteins opens several fields of future diagnostic and therapeutic research that would improve management of congenital toxoplasmosis.