Purpose: Teratogens cause birth defects and malformations while human development is being completed. In pregnancy, urinary tract infection (UTI) is a common health problem caused by bacteria. The fluoroquinolones such as ciprofloxacin, levofloxacin, moxifloxacin, and gemifloxacin can treat various types of bacterial infections successfully. The aim of this study is to determine whether the use of ciprofloxacin during pregnancy causes oxidative stress on brain tissues of the fetus, and whether quercetin contributes to prevent this damage if stress has already occurred.Materials and methods: In our study, 22 young female Wistar albino rats weighing 250g were used. Rats were mated overnight in separate plastic cages. Female rats were regarded as pregnant when a vaginal plug was observed, and these were divided into four groups of control, ciprofloxacin, quercetin, and cipro+quercetin. Two daily i.p. 20mg/kg doses of ciprofloxacin were administered to ciprofloxacin group between 7 and 17 d of pregnancy. Throughout the study, daily (20 d) 20mg/kg quercetin was dissolved in corn oil and administered to the quercetin group by oral gavage. Rats were fed ad libitum throughout the study. Fetuses were taken by C-section on the 20th day of pregnancy. Thereafter, the brain tissues were subjected to histological assessments and biochemical analyzes.Results: The experimental groups were compared with the control group; ciprofloxacin affected fetal development, especially caused damage to neurons in brain tissue and cause hemorrhagic defects. And also, it was determined that many parameters were affected such as antioxidant parameters, enzyme levels and levels of malondialdehyde (MDA) (a marker of lipid peroxidation). Quercetin is a member of flavonoid with strong antioxidant properties, and our results indicate that the use of ciprofloxacin in pregnancy can result damage to fetal brain tissue.Conclusions: Unlike these results when some parameters are evaluated it is understood that this harmful effects suppressed by quercetin.