Objective To study the colonization rate and antibiotic resistance of group B Streptococcus (GBS) in gravidas during late pregnancy,and to evaluate the effectiveness of GBS screening in late pregnancy and intrapartum antibiotic prophylaxis (IAP) for the prevention of neonatal early-onset GBS disease (EOGBS).Methods A retrospective study was conducted to analyze the colonization rate and antibiotic resistance pattern of GBS in 14 204 gravidas who were screened for GBS at 35-37 gestational weeks during March 2016 to March 2018 in the University of Hongkong-Shenzhen Hospital (HKU-SZH).Differences in the incidence of EOGBS before and after GBS screening and IAP were analyzed using Chi-square or Fisher's exact test.Results Among the 14 204 gravidas,2 027 cases were GBS positive with a colonization rate of 14.27％.Incidence rates of EOGBS before and after GBS screening were 0.6‰ (4/6 356) and 0.07‰ (1/14 403),respectively (Fisher's exact test,P=0.033).GBS isolates were 100％ (2 027/2 027) sensitive to penicillin and vancomycin.Resistance rates to clindamycin and erythromycin were 67.2％(1 363/2 027) and 65.7％ (1 332/2 027),respectively.Conclusions Routine GBS screening in late pregnancy and IAP can significantly decrease the incidence of EOGBS.Penicillin is the optimal choice for prevention and treatment of GBS infection.