Background: Despite major advances in perinatal care, preterm delivery (PTL) is still the predominant cause of perinatal mortality and a major cause of neurological morbidity in surviving infants. Objective: the objective of this study is to find any association between maternal group B streptococcus (GBS) colonization and preterm delivery. Patients and Method: This study is a prospective study including 100 pregnant women between 28 – 36 weeks of gestation from those who attended the Emergency Department at Al-Galaa Maternity Teaching Hospital from April 2015 to August 2015. All patients were tested for genital colonization with Group B streptococcus (GBS) by taking low vaginal swab that was sent for microbiological examination. Results: In this study there was a significant difference between positive and negative cases as regard obstetric data. As regard preterm labor, 80% of positive swab cases had preterm labor compared to 46.2% of negative swab cases and this was statistically significant. Positive vaginal swab cases are at 7 times higher risk to have preterm labor compared to negative cases. Conclusion: GBS vaginal colonization was associated with premature labour in the studied population. Women with GBS vaginal colonization qualify for intrapartum chemoprophylaxis. The study results suggest that the early prenatal screening for GBS may identify pregnant women at risk of PTL.