ObjectiveStreptococcus agalactiaeis an important pathogen in neonates and pregnant women. Neonatal invasive infections due toS. agalactiaeare life-threatening and preventive strategies for this challenge of human have become a concern. The aim of the present study was to determine the prevalence of rectovaginal colonization, related risk factors and antibiotic resistance pattern ofS. agalactiaeamong pregnant women in Iran.MethodsThe present study was performed on 240 pregnant women. Vaginal and rectal swabs were obtained from all of the women and then were transferred to the laboratory. The isolation and identification ofS. agalactiaewas performed by standard microbiological tests and polymerase chain reaction (PCR) assay. The antimicrobial susceptibility patterns of the isolates were determined by the Kirby-Bauer disk diffusion. Polymerase chain reaction was used to detectermBandmefAgenes in erythromycin-nonsusceptible isolates.ResultsOut of 240 pregnant women, 16 cases (6.7%) were colonized byS. agalactiae. There is no significant association between demographic-obstetric factors and maternalS. agalactiaecolonization in the pregnant women. Linezolid, vancomycin and ampicillin were the most effective antibiotics againstS. agalactiae. TheermBgene was present in 6 (35.29%)S. agalactiaeisolates. However, themefAgene was not detected in any of the isolates.ConclusionGiven the relatively significant prevalence ofS. agalactiaecolonization in the pregnant women in the present study and the risk of serious neonatal infections, the screening of pregnant mothers for the bacteria seems necessary. Our findings highlight the importance of appropriate antibiotic prophylaxis during pregnancy for the prevention of early onsetS. agalactiae-neonatal infection and comorbidity.