Objective: To investigate whether the cervical mucus in pregnants has antimicrobial activity in vitro and to determine its relationship with prognosis of pregnancy. Material and Methods: Cervical mucus samples were collected from 50 women with single pregnancy during the first trimester. Sterilized Wartman papers were soaked into mucus samples and dried under sterile conditions. Culturing was performed by disk diffusion method which uses Miller Hinton medium and Mac-Farland 0.5 solution prepared with Staphylococcus amens, Escherichia colt, Klebsiella pneumonia and Candida albicans. Positive or negative zones were determined by measuring the diameters of inhibition zones occurred following 18 hours incubation period. Prognosis of pregnants with or without antimicrobial effect of cervical mucus were compared. Results: In 28 cases, it was demonstrated that cervical mucus had antimicrobial effects. During the follow-up period of 27 pregnants, 22(81.5%) gave viable birth in term, 3 (11.1%) had abortus, and 1 (3.7%) had early membrane rupture at 36th week of gestation. In 22 cases, cervical mucus showed no antimicrobial effect. 20 of these followed-up and 14 (70.0%) participants gave viable birth at term, 3 (15.0%) had abortus, and 2 (10.0%) had preterm delivery. There was no statistically significant difference between the two groups in terms of pregnancy prognosis. Conclusion: Cervical mucus prevents infections from vagina to upper genital organs not only mechanically but also by functioning as a chemical barrier. In our study, it is established that presence or absence antimicrobial effect of mucus does not have a significant impact on the prognosis of pregnancy. We think that studies with greater number of participants may give different results.