Recommendations for IAP to prevent perinatal GBS disease were issued in 1996 by the CDC. In these guidelines, the use of one of two prevention methods was recommended: either a risk-based approach or a culture-based screening approach. The CDC issued updated guidelines in 2002; these guidelines recommended the universal culture-based screening of all pregnant women at 35–37 weeks' gestation to optimize the identification of women who must receive IAP. CDC also recommended that women with unknown GBS colonization status at the time of delivery be managed according to the presence of intrapartum risk factors. Because of this strategy, the US has seen a major reduction in the incidence of GBS-EOD.