Objective: This study assessed blood C-reactive protein (CRP), fibrinogen, procalcitonin, and CA125 levels and determined whether they have an effect on pregnancy. Material & Methods: Between Feb. and Sep. 2018, 50 consecutive women who had their first frozen embryo transfer at a tertiary referral IVF center in Turkey were included in the study. Serum samples were collected on the second day of the cycle and on the transfer day. The women were divided into two groups based on the results of pregnancy outcome: pregnant (group 1) and non-pregnant (group 2). Blood CRP, fibrinogen, procalcitonin, and CA125 levels were compared between the groups. Results: There were no statistically significant differences between the groups according to CA125, CRP, fibrinogen, and procalcitonin levels at the beginning of the cycle and on the transfer day. In comparison with levels at the beginning of the cycle and on the transfer day, fibrinogen and CRP were significantly higher on the transfer day than at the beginning of the cycle. Procalcitonin was significantly higher on the transfer day than at the beginning of the cycle in group 1. However, there was no statistically significant difference between the transfer day and the beginning of the cycle in group 2. Conclusions: However, the fibrinogen, CRP and procalcitonin levels were significantly higher on the transfer day than at the beginning of the cycle. The results indicated that acute phase reactants or CA125 should not be used to determine the time of embryo transfer or predict pregnancy.