The aim of the present study was to describe whether abnormal cervical mucus discharge (A-CMD) or pathogens in cervical mucus discharge (CMD) have effects on reproductive performance of cows and heifers in estrus. Animals having clear discharges (68 cows, 38 heifers) with normal viscosity and without bad odor were grouped as normal cervical mucous discharge (N-CMD) group. The other animals (84 cows, 32 heifers) were grouped as A-CMD group. Microorganisms isolated from samples were divided into three groups as uterine pathogens (UP), potential uterine pathogens (PUP) or opportunistic uterine pathogens (OUP). Presence of PUP was associated with A-CMD for both cows (p<0.01) and heifers (p<0.02). First service conception rates (FS-CR) were lower in cows positive for PUP (p<0.01). Moreover, presence of PUP and OUP affected FS-CR in heifers (p<0.01). Although A-CMD significantly affected FS-CR in cows (p<0.04), it did not affect FS-CR in heifers. Differences in average open day for cows (p<0.02) and first service age for heifers (p<0.01) were significant between N-CMD and A-CMD groups, respectively. The current study suggested that CMD should be evaluated more carefully when there are infertility problems. In addition to the known microorganism that causes sterility and infertility in the UP group, pathogens in the PUP group should be considered for their potential to cause infertility.