This new recommendation provides a five-week window  for valid culture results that includes births that occur up to a gestational age of at least 41 weeks. The culture-based screening approach is followed in most developed countries such as the United States,  France, Spain, Belgium, Canada, Argentina, and Australia. The risk-based strategy is followed in the United Kingdom, and the Netherlands. Screening for GBS colonization
Though the GBS colonization status of women can change during pregnancy, cultures to detect GBS carried out ≤5 weeks before delivery predict quite accurately the GBS carrier status at delivery. In contrast, if the prenatal culture is performed more than five weeks before delivery it is unreliable for predicting accurately the GBS carrier status at delivery.The clinical specimens recommended for culture of GBS at 36–37 weeks’ gestation, this recommendation provides a 5-week window for valid culture results that includes births that occur up to a gestational age of at least 41 weeks  (32–34 weeks of gestation for women with twins) are swabs collected the lower vagina (near the introitus) and then from the rectum (through the anal sphincter) without use of a speculum. Vaginal-rectal samples should be collected using a flocked swab preferably, since flocked swabs releases samples and microorganisms more effectively than fiber swabs. Following the recommendations of the Centers for Disease Control and Prevention of United States  (CDC) these swabs should be placed into a non-nutritive transport medium and later inoculated into a selective enrichment broth, Todd Hewitt broth with selective antibiotics  (enrichment culture).
These factors include onset of labor before 37 weeks of gestation (premature birth), prolonged rupture of membranes (≥18h before delivery), intra-partum fever (>38 °C,  >100.4 °F), amniotic infections (chorioamnionitis), young maternal age, and low levels of GBS anticapsular polysaccharide antibodies in the mother. Nevertheless, most babies who develop EOD are born to GBS colonized mothers without any additional risk factor. A previous sibling with EOD is also an important risk factor for development of the infection in subsequent deliveries, probably reflecting a lack of GBS polysaccharides protective antibodies in the mother. Heavy GBS vaginal colonization is also associated with a higher risk for EOD. Overall, the case–fatality rates from EOD have declined, from 50% observed in studies from the 1970s to 2 to 10% in recent years, mainly as a consequence of improvements in therapy and management. Fatal neonatal infections by GBS are more frequent among premature infants.GBS LOD affects infants from 7 days to 3 months of age and is more likely to cause bacteremia or meningitis. LOD can be acquired from the mother or from environmental sources. Hearing loss and mental impairment can be a long-term sequela of GBS meningitis. In contrast with EOD, the incidence of LOD has remained unchanged at 0.26 per 1000 live births in the US. S. agalactiae neonatal meningitis does not present with the hallmark sign of adult meningitis, a stiff neck; rather, it presents with nonspecific symptoms, such as fever, vomiting and irritability, and can consequently lead to a late diagnosis.