1. Perinatal infections occur during labor and delivery when microbial agents infect the infant. The most common sources are the maternal genital tract and amniotic fluid. 2. The newborn is initially colonized by microbes on the skin and mucosal surfaces, which sometimes cause illness by direct extension or bloodstream invasion. 3. Risk factors for neonatal sepsis include low birth weight, premature rupture of membranes, and maternal infection. The most common causes are Group B Streptococcus and E. coli from the maternal genital tract.