Purpose: To investigate the morphological and biochemical effects of lamivudine associated with ritonavir on maternal and fetal livers and kidneys throughout the pregnancy of albino rats. Materials and Methods: Forty pregnant rats were divided into four numerically equal groups: control (C), experiment 1 (E1), experiment 2 (E2), and experiment 3 (E3). Only distilled water was given to the control group, while groups E1, E2, and E3 received, respectively, 5, 15 and 45 mg/kg of lamivudine associated with 20, 60, and 180 mg/kg of ritonavir, per day, throughout the pregnancy. On the 20^th day of the pregnancy, the histological structure of the maternal and fetal livers and kidneys was analyzed by means of optical microscopy, along with the blood concentrations of AST, ALT, urea, and matrix creatinine. The numerical variables were analyzed using the Kruskal-Wallis test and Dunn’s multiple comparison test. Results: The histological alterations occurred in both the maternal livers and the maternal kidneys, particularly in group E3, which received the greatest therapeutic dosage (nine times). The blood levels of ALT in group E3 were significantly lower than in the other groups (p = 0.0037). The urea and creatinine levels in the blood were significantly lower in group E1 (p = 0.0420 and p = 0.0108, respectively). Conclusions: The association of lamivudine and ritonavir affected the histological structure of the kidneys of the matrices of group E3. There was a significant decrease in the blood values of urea e creatinine in group E1.