strate vertical GBS transmission. Of these, only 1% to 8% develop invasive disease (Garland & Fliegner, 1991, p. 121). The incidence of early onset GBS disease is approximately 1.9 to 3.7 per 1,000 live births. It is characterized primarily by sepsis and pneumonia. Only about 20% to 30% of affected infants develop meningitis, however 50% of GBS meningitis survivors do exhibit significant neurological sequelae. Symptoms often become clinically apparent within 6 hours of birth. The mortality rate for this condition has been estimated at 15% to 25% (ACOG Tech. Bull. #170, 1993, p. 55).
Under certain circumstances, the attack rate of early onset GBS disease may increase dramatically. For example, in babies born to mothers with perinatal vaginal colonization, the attack rate is 10 per 1,000 live births. However, in mothers with heavy GBS colonization, that rate may climb to 40 per 1,000 live births. The rate is also higher for premature infants. Infants whose birth weight is less than 1,000 grams are 7.3 times more likely to develop early onset GBS
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