Background/aim: The negative impact of oxidative stress on oocytes obtained from in vitro fertilization (IVF) patients is a challenge for the optimization of live birth rates. In this study, it is aimed to investigate whether oxidant/antioxidant parameters have a predictive value in terms of determining the count and quality of oocytes. Materials and methods: Catalase (CAT), glutathione-S-transferase (GST), arylesterase (ARE) enzyme activities, and malondialdehyde (MDA) levels were analysed in cumulus cells of poor responder (n = 28, oocyte count <_ 4), normo responder (n = 48, 5 <_ oocyte count <_ 14), and high responder (n = 26, oocyte count >= 15) patient groups continuing IVF treatment. Results: The cumulus cell GST enzyme activity were statistically significantly increased in the high responders group compared to the poor responder and the normo responder's groups (p < 0.001 and p = 0.002, respectively). The cumulus cell MDA levels were significantly decreased in the high responder group compared to the poor responder group (p = 0.008). The cumulus cell CAT (p = 0.175) and ARE (p = 0.124) enzyme activities were examined but no statistically significant difference found between the groups. Conclusion: The significant increase in GST enzyme activity and significant decrease in MDA levels in the high responder group indicate that oxidative stress has an effect oocyte status and quality.