Around one in four people is carrying around the bacterium called group B streptococcus, generally in the intestines or in the genitalia. The good news is that for most adults, the bacterium is harmless. It causes no symptoms and does no damage to the body, to the point that carriers of the bacterium are often described as “colonized” rather than infected. However adults with chronic illnesses such as diabetes, or who are seniors, can be affected; when adults are sickened by it, it usually causes pneumonia, skin infections, or infections of the bones or joints, and more rarely meningitis. Furthermore, pregnant women are at high risk of passing it on to their children during labor—group B strep illness affects one in every 2,000 infants born in the United States
These infants can start to develop symptoms as soon as 12 hours after birth, or it may take a few months. This can actually be more frightening, if the child becomes lethargic, has difficulty feeding, develops a fever, and starts to have seizures when you’re already home from the hospital and starting to get used to your life with your newborn. Women are typically tested for group B strep colonization at around 35 weeks of pregnancy. Later than that might be too late to be useful; earlier than that might be too early to give accurate information about the mother’s status at the time of labor.
That’s why babies born prematurely, at earlier than 37 weeks, are considered at high risk for group B strep infection. Other risk factors include the mother having a fever over 100 during labor or the baby having a rapid heartbeat, long labor when water breaks more than 18 hours before delivery, urinary tract infection, or infection of the placenta called chorioamnionitis. Multiple births are also at higher risk, and someone who has had a baby with group B strep infection before is likely to do so again.
Fortunately, even in high-risk deliveries, doctors can give antibiotics intravenously to help prevent transmission of the group B strep bacteria. Penicillin is most commonly used, with substitutions if the mother is allergic or it’s likely that the baby is. A woman who has tested positive for group B strep should make sure her delivery team knows about it so that appropriate precautions can be taken.