Group B streptococcus infections may be serious for the neonates. The infection can occur during the birth, by contact with the genital area. That is why the detection of this bacteria is systematically realised in pregnant women between 34 and 37 weeks of amenorrhea in order to give prophylactic antibiotic treatment in case or positive carriage. This strategy presents 2 disadvantages : (1) detection of the group B streptococcus at 34 and 37 weeks of amenorrhea in not predictive of a carriage at delivery, (2) many pregnant women escape from systematic screening, leading to a systematic antibiotic treatment, which means useless costs, and useless antibiotic exposure with resistant bacteria selection. Real time polymerase chain reaction (PCR) allows a rapid detection anytime with no specific microbiological qualification. The aim of the study is to assess the economic outcomes of this strategy and the epidemiological values for St Etienne hospital.