Abstract： Objective To study the sensitivity of the real-time polymerase chain reaction (RT-PCR) in detecting group B streptococcus (GBS) in late pregnant women and the influence of vaginal/rectal GBS colonization on maternal and neonatal outcomes. Methods Microbiological culture and RT-PCR for GBS were both performed for each sample taken from the vagina and rectus in 617 gravidas at 35-37 weeks of gestation, with an average age of 30.1, among which 80 aged over 35. Forty-one out of the 617 women were multiparous and 576 primiparous. The laboratory results were collected and the pregnant outcomes were followed. Results (1) Out of the 617 gravidas, 21 (3.4%) were GBS positive by culture (all positive in RT-PCR) and 57 (9.2%) were GBS positive by RT-PCR. Thirth-six cases with PCR positive but culture negative results were analyzed by sequencing, and 34 showed GBS positive and 2 negative. (2) The sensitivity and specificity of RT-PCR was 100% (55/55) and 99.6% (560/562) respectively. (3) The average age of GBS positive gravidas was 30 ± 4, without significant difference compared with that of GBS negative women (31±4), P>0.05. The GBS positive rates were also similar between the primiparas and the muliparous [7.3% (3/41) vs.9.4% (54/576)] , between elderly women and those under the age of 35, and between those women who had abortions over and less than 3 times (all P>0.05). (4) No significant difference was found in the cesarean section rate between the GBS postitive and negative group [54.4% (31/57) vs.44. 6% (250/560), P>0.05]. (5) Compared with the GBS negative group, the GBS positive group had higher incidence of intrauterine infection [6.6% (37/560) vs. 15.8% (9/57)], postpartum hemorrhage (2.9% vs.10.5%) and fetal distress (25.9% vs. 38.6% ) all P <0.05, but had similar incidence of premature rupture of membranes [25.0% (140/560) vs. 33.3% (19/57) ], pretcrm birth and meconium-stained amniotic fluid. (6) The neonatal infection rate in the GBS positive group was significantly higher than that of the GBS negative group [29.8% (17/57) vs. 13.2% (77/560), P < 0.05]. One neonate in the GBS positive group developed early-onset severe GBS infection and achieved better outcome under proper treatment. Conclusions Maternal GBS carrier at 35-37 weeks of gestation can lead to adverse pregnant outcomes by increasing the incidences of intrauterine infection and neonatal infections. However, RT-PCR could be a routine method to detect GBS status in late pregnant women with its higher sensitivity and specificity.