How many women can benefit from a full intrapartum antibiotic prphylaxis for prevention of perinatal group B streptococcal disease?

Background: In Belgium as in many Western countries, GBS are still the leading cause of severe perinatal infections. Current guidelines for prevention recommend intrapartum antimicrobial prohylaxis (IAP)
administered promptly before delivery to pregnant women colonized with GBS. The risk of vertical GBS transmission to the newborn decreases as the duration of prophylaxis increases. The considered threshold for
prophylaxis adequacy is the first dose administered at least 4 hours before delivery.
Objective: To evaluate the proportion of pregnant women who could benefit from an adequate IAP for the prevention of GBS perinatal infections.
Methods: Between June and October 2003, we recorded in two hospitals the elapse time between admission for labor and delivery. We assumed 5 hours represent a useful threshold to allow admission, revision of chart and administration of adequate IAP. The status of vaginal colonization with GBS
was determined by CDC’s recommended culture method with Granada agar added.
Results: Among 532 women, 27.3 % delivered within 5 hours after admission for labor. The colonization rate for GBS was 25.6 %. The distribution of elapse time between admission and delivery for GBS
colonized pregnant women was not significantly different from non colonized women (p <= 1).
Conclusions: 1) With the current prevention strategy, 27.3 % of these pregnant women would not have benefit from adequate prophylaxis 2) These results highlight the importance of an efficient organization to
warranty prompt administration of IAP as soon as possible when mandatory. 3) If a rapid intrapartum screening test is used, no delay can be afforded “from ward to bench to bed”.