Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) infection has a significant clinical impact on both pregnant women and neonates. The aim of this study was to accurately assess the vertical transmission rate of MRSA and its clinical impacts on both pregnant mothers and neonates.Material and Methods: We conducted a prospective observational cohort study of 898 pregnant women who were admitted to our department and 905 neonates from August 2016 to December 2017. MRSA was cultured from nasal and vaginal samples taken from the mothers at enrollment and from nasal and umbilical surface swabs taken from neonates at the time of delivery. We examined the vertical transmission rate of MRSA in mother-neonate pairs. We used multivariable logistic regression to identify risk factors for maternal MRSA colonization and maternal/neonatal adverse outcomes associated with maternal MRSA colonization.Results: The prevalence of maternal MRSA colonization was 6.1% (55 out of 898) at enrollment. The independent risk factors were multiparity and occupation (healthcare provider) (OR: 2.35, 95% CI: 1.25-4.42, OR: 2.58, 95% CI: 1.39-4.79, respectively). The prevalence of neonatal MRSA colonization at birth was 12.7% (7 out of 55 mother-neonate pairs) in the maternal MRSA-positive group, whereas it was only 0.12% (one out of 843 pairs) in the maternal MRSA-negative group (OR: 121, 95% CI: 14.6-1000). When maternal vaginal samples were MRSA positive, vertical transmission was observed in four out of nine cases (44.4%) in this study. Skin and soft tissue infections (SSTIs) developed more frequently in neonates in the maternal MRSA-positive group than in the MRSA-negative group (OR: 7.47, 95% CI: 2.50-22.3).Conclusions: The prevalence of MRSA in pregnant women was approximately 6%. Vertical transmission caused by maternal vaginal MRSA colonization was observed in four out of nine cases (44.4%). Although our study includes limited number of maternal MRSA positive cases, the vertical transmission of MRSA may occur in up to 44% of neonates of mothers with vaginal MRSA colonization. Maternal MRSA colonization may associate with increased development of SSTIs in neonates via vertical transmission.