Objective: This study aims to evaluate the risk factors for group B streptococcal infection and their frequency amongst obstetrical patients during last trimester. Methods: It is a cross sectional, prospective study conducted at Lady Willingdon Hospital, Lahore during October 2015 to March 2016. 200 patients were selected with age group more than 20 years, their lower vaginal swabs were taken. Those taking antibiotics, ruptured membranes, chronic infection or disease and vaginal bleeding were excluded. Swab cultures for GBS (group B streptococci) was performed and frequency of positive swab cultures was noted. SPSS 20 was used for data analysis. Chi square test was applied for association. P value of less than 0.05 was considered significant. Results: All cases had mean age between 26.3±4.3 years and gestational age was 35.5±2.6 weeks. Infection frequency was 14%. There was a strong association between abortions ratio and parity with p value of 0.01 and 0.03 respectively. The association between vaginal discharge and GBS infection had p value of 0.02 which was statistically significant. Key words: Group b streptococcal infection, Vaginal discharge, Last trimester, obstetric.