The complications arise when a woman colonized with GBS gives birth. The GBS can, under certain circumstances, cause a life threatening infection in the baby. Most of them will never know they are colonized, because GBS usually is a benign bacteria. GBS disease of the newborn is a very serious infection. GBS disease usually develops in the first few hours after birth, although symptoms sometimes take a week to appear.
Premature babies are more fragile and more at risk for complications after birth.
They are also more at risk for GBS infection and more likely to have a serious infection than full-term babies. GBS disease occurs in 2 out of every 1000 newborn babies. Unfortunately, because of the nature of the GBS bacteria, cultures are not always accurate in assessing colonization. It is possible for a colonized women to have a positive culture one day and a negative one the next. Some of this is due to difficulties with the culture itself, and some of it seems to relate to variations in the number of bacteria present at any specific time.