Objective: To determine the proportion of pregnant women with presumptive preterm labor who had positive culture of genitourinary tract microorganisms and to determine the relationship of positive genitourinary infection and pregnancy outcomes.

Material and Method: This retrospective cohort study was performed at Department of Obstetrics and Gynecology, Faculty of Medicine, Siriraj Hospital, Mahidol University. Medical records of pregnant women with presumptive preterm labor who were admitted in non-private labor room between January 2003 and December 2008 were reviewed. Characteristics, results of vaginal swab culture and urine culture, and clinical outcomes were analyzed and reported.

Results: The prevalence of positive culture of genitourinary tract microorganisms in presumptive preterm labor-women (total n = 704) was 24.3% (95% CI = 21.3-27.6), 22.1% (95% CI = 19.1-25.4) of vaginal swab culture and 5.3% (95% CI = 3.8-7.2) of urine culture. However, only 9.8% were pathologic organisms. There were no statistically significant differences in characteristics and rate of preterm labor between women with a positive and a negative culture. Moreover, there were no statistically significant differences in characteristics and preterm birth outcomes between women in both groups.

Conclusion: There were no clinical significances of positivity of pathologic bacteria from genitourinary tract as a predictor of preterm delivery and its outcomes. Although the prevalence is quite high, the value of these screenings is still questionable.

Keywords: Presumptive preterm labor, Vaginal swab culture, Urine culture