To evaluate the performance of laboratory tests for pregnant women during prenatal care at five UBS of Pelotas / RS. Descriptive study of quantitative, using secondary data. The sample consisted of 392 chips prenatal pregnant women with probable date of delivery in 2007. The basic laboratory tests were analyzed: hemoglobin / hematocrit (Hb / Ht), Rh factor, VDRL, Blood Glucose, Urine (Type I), Anti-HIV, HBsAg, Toxoplasmosis. Data analysis showed a high percentage of lack of records and the eight tests analyzed only four (50%) had filled in more than half of the sample. Thus, they are concerned about the high percentage of non-registration of variables related to maternal complications important, such as anemia, urinary tract infections, diabetes mellitus, syphilis and HIV testing. It is expected that the evaluation can contribute to improving the quality of prenatal care offered to users of the Unified Health System in the city and also assist in the management and organization of the Program of Prenatal Care.Descriptors: assessment; prenatal care; laboratory tests.