Aims: determining the cut-off value for a homebased ELISA assay for IgG avidity at the Biomedical Research Centre at the Universidad del Quindio and correlating the results from pregnant females’serum samples with IgM and IgA test results. Material and methods: 17 patients having known infection dates were studied to determine the receptor operator curve (ROC) for a home-made avidity assay. 91 sera samples from pregnant females were also analysed at the same laboratory for IgM and IgA anti Toxoplasma antibodies. Results: 100% sensitivity and 88% specificity were obtained by using a 30% avidity cut-off value for identifying infections acquired less than 4 months beforehand. 63% of the 91 pregnant females had less than 16 weeks’ gestation at the time of examination and three of the patients had low avidity tests (<30%). Only one case had avidity less than <30% after 8 months’ infection. The avidity test was requested before the 16th week of the gestational period for most of the patients. Conclusions: a 30% cut-off identified sera containing infections having less than 4 months’ evolution.