Abstract :Serodiagnosis of toxoplasmosis is usually achieved by the detection of IgG and IgM against
Toxoplasma gondii. Routinely the detection of IgM antibodies is an acute phase indicator, but in the
case of this disease, this isotype can persist even after years of this initial phase of infection, which
represents many disadvantages during the diagnosis early of the congenital transmission, that occurs
when an infected pregnant woman transmits the parasite to her unborn baby. Numerous researchers
have conducted studies to detect recent infections that arise in an unapparent way, without clinical
symptoms (asymptomatic), in newborns or fetus infected by congenital route, which due to the lack
of administration of a rapid and timely chemotherapeutic treatment can present severe pathological
damages, and even, trigger in the death. Serological tests can present difficulties in differentiating
acute cases of chronic infections. The IgG avidity test has been developed to distinguish between
latent acute and infections in pregnant women who present a mixture of IgG isotypes and IgM
anti-T. gondii. It is an important additional tool that saves time and money in the diagnosis of
infections in women during pregnancy, as well as favors an accurate clinical management because it
allows determining the toxoplasmosis phase safely and effectively.