Group B Streptococcus (GBS) or Streptococcus agalactiae is a species of the normal flora of female urogenital tract. Although GBS colonization usually does not cause problems in healthy women before pregnancy, it can lead to serious illness for the mother and newborn. GBS-colonized mothers are at risk for chorioamnionitis, endometritis and postpartum infection. Moreover, GBS carriage is associated with adverse pregnancy outcomes such as stillbirth, preterm delivery and premature rupture of the membrane. Newborns who are infected with GBS may develop neonatal sepsis and meningitis. Invasive GBS infection is associated with significant morbidity and mortality among pregnant women and their neonates through the world. Thus, identification of GBS-colonized women is critical for prevention of neonatal GBS infection. According to the prevention guidelines, universal prenatal screening tests for identification of GBS carrier mothers are advised. This study investigated the prevalence of GBS in pregnant women and evaluated the PCR assay for detection of the GBS in comparison with a specific culture method.This provides a rapid and precise technique for GBS diagnosis during labor.