Around one in four expectant mothers carries a bacterium called group B streptococcus. The bacterium, which is generally found in the intestines or the vagina, is harmless in adults, but can harm the developing fetus. It can cause miscarriage or stillbirth, lead to preterm delivery, and cause significant, sometimes fatal health problems after the child is born. These effects can in some cases last a lifetime.
The good news is that the incidence of these effects is going down. However, it is still a problem that affects a substantial number of infants and newborns every year—one in 1,200 newborns under a week old show signs of infection, along with a number of stillbirths and miscarriages. Moreover, women who are found to be carrying the bacterium in their first pregnancies are more likely to be carrying it again subsequently.
One common affect, when the child is born otherwise healthy, is meningitis. Over the past quarter century, more of these children have been surviving meningitis caused by group B strep, but it still reverberates. In a recent study, nearly half of subjects who, as infants, had been diagnosed with group B streptococcal meningitis were found to have some kind of lasting neurological damage or impaired functioning. Nearly one in five of those subjects had severe damage, such as cerebral palsy or impaired vision or hearing.
It is recommended that pregnant women get tested for group B strep at around 36 weeks, since it’s almost always asymptomatic in women. That is the best time to deal with it—the use of antibiotics during labor drops the risk of infecting the baby from one in 200 to one in 4,000, a 95 percent reduction. These antibiotics are given intravenously if there’s a positive test or if the mother has had group B strep in the past, if the baby is at least three weeks premature, if labor is taking longer than 18 hours, or if the mother develops a fever during labor. After birth, if there’s some reason to suspect a group B strep infection, a blood or spinal fluid test can be done, though it takes most of the week.