Fig 1 Flow diagram showing sequence of events included in the cost effectiveness model. The 12 maternal risk groups are divided into preterm and term deliveries. Preterm deliveries: 1, planned caesarean section; 2, previous baby with group B streptococcal disease; 3, positive urine or vaginal swab for group B streptococci in current pregnancy; 4, fever ≥38.0°C during labour; 5, membrane rupture ≥2 hours before labour starts; 6, membrane rupture <2 hours before labour starts. Term deliveries: groups 7 to 10, equivalent to preterm groups 1 to 4; 11, membrane rupture for ≥18 hours; 12, no risk factors. The risk groups are exclusive and are in hierarchical order. (GBS=group B streptococcal infection, IV=intravenous, PCR=polymerase chain reaction.)