Abstract Background Uganda has registered a reduction in new HIV infections among children in recent years. However, mother-to-child transmission of HIV still occurs, especially among pregnant women who present late. To eliminate this transmission, all HIV-positive pregnant women should be identified during antenatal HIV testing. We described women newly identified HIV-positive during pregnancy and postnatal period 2015–2018. Methods We extracted surveillance data for women identified as HIV-positive during pregnancy and the postnatal period reported through the Health Management Information System from 2015–2018. We calculated proportions newly positive at antenatal, labor, and postnatal periods nationally and at district levels. We disaggregated data into ‘tested early’ (during antenatal care) and ‘tested late’ (during labor or postnatal period) and calculated the proportion positive. We evaluated trends in these parameters at national and district levels. Results Overall, 8,485,854 mothers were tested for HIV during this period. Of these, 2.4% tested HIV-positive for the first time. While the total number of mothers tested increased from 1,327,022 in 2015 to 2,514,212 in 2018, the proportion testing HIV-positive decreased from 3.0% in 2015 to 1.7% in 2018 (43% decline over the study period, p