Bacteria are almost always the cause of sepsis in newborns and infants. Bacteria such as E. coli, Listeria monocytogenes, Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae type b, Salmonella, and Group B streptococcus (GBS) are the more common culprits in sepsis in newborns and infants younger than 3 months.
Premature babies receiving neonatal intensive care are particularly susceptible to sepsis because their immune systems are even more underdeveloped than other babies, and they typically undergo invasive procedures involving long-term intravenous (IV) lines, multiple catheters, and breathing through a tube attached to a ventilator. The incisions an infant gets for catheters or other tubes can provide a path for bacteria, some of which normally live on the skin's surface, to get inside the baby's body and cause an infection.
In some cases of sepsis in newborns, bacteria enter the baby's body from the mother during pregnancy, labor, or delivery. Some pregnancy complications that can increase the risk of sepsis for a newborn include:
- maternal fever during labor
- an infection in the uterus or placenta
- premature rupture of the amniotic sac (before 37 weeks of gestation)
- rupture of the amniotic sac very early in labor (18 hours or more before delivery)
Some bacteria (GBS in particular) can be acquired by the newborn during delivery — 15 to 30% of pregnant women carry the bacterium for GBS in the vagina or rectum, where it can be passed from mother to child during delivery.