What's the difference between early-onset and late-onset neonatal sepsis?

Early-onset and late-onset neonatal sepsis both involve a bacterial infection that overwhelms the infant's immune system. By definition, early-onset sepsis occurs within the first week after birth, whereas late-onset sepsis occurs after the first week (but usually in the first three months). The infection in early-onset sepsis is usually transmitted from the mother, either in utero due to disease or damage, or in childbirth, due to infections in the birth canal or rectum. Late-onset sepsis is acquired from the infant's surroundings: frequently, it can result from other procedures the baby gets in the hospital.