The aim of the research was to investigate the effect of aminoguanidine on the content of autoantibodies in the serum, nitric oxide synthesis (NO), glial fibrillary acidic protein (GFAP) content and indicators of free radical oxidation in the cerebral hemispheres of BALB/c mice with antiphospholipid syndrome (APS) on the 18th day of pregnancy. An increase in the content of autoantibodies to brain proteins (120 kDa, 150 kDa, and >170 kDa) was detected in the serum of BALB/c mice with APS on the 18th day of pregnancy. An increase in the content of GFAP (total), GFAP (49-37 kDa), NO2¯, NO3¯ and prooxidant-antioxidant system imbalance in the cerebral hemispheres of pregnant mice with APS was established. With administration of aminoguanidine into the pregnant mice with APS, a decrease in the content of autoantibodies to brain proteins (120 kDa and 150 kDa) in serum was proved. With the introduction of aminoguanidine, a selective inhibitor of inducible NO synthase on the 18th day of pregnancy the increase in GFAP (49-37 kDa) in the cerebral hemispheres of APS mice was established, and the GFAP (total), NO2¯ and NO3¯ content did not change significantly, relative to the indicators of pregnant animals with APS. With introduction of aminoguanidine in cases of APS on the 18th day of pregnancy lesser manifestations of oxidative stress in the cerebral hemispheres, a decrease in the activity of lipid peroxidation processes, an increase in the activity and content of the antioxidant system components was evidenced. Thus, aminoguanidine has a neuroprotective effect in obstetric antiphospholipid syndrome in the BALB/c mice.