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Antenatal screening for Group B Streptococcus: a diagnostic cohort study.
Janet E Hiller1, Helen M McDonald, Philip Darbyshire
1Department of Public Health, University of Adelaide, Adelaide, 5005, Australia. janet.hiller@adelaide.edu.au
BMC Pregnancy and Childbirth
|July 27, 2005
Summary
Delaying Group B Streptococcal (GBS) screening until 36 weeks gestation improves detection of colonization. A single vaginal swab is as effective as combined swabs for GBS screening in pregnant women.
Area of Science:
- Obstetrics and Gynecology
- Infectious Diseases
- Microbiology
Background:
- Strategies to prevent early-onset Group B Streptococcal (GBS) sepsis are crucial.
- GBS infection is acquired vertically from mother to infant.
- Optimizing GBS screening timing and methods is essential for prevention.
Purpose of the Study:
- To establish scientific evidence for optimal GBS screening timing and methods in Australia.
- To compare the predictive value of GBS screening at 35-37 weeks versus 31-33 weeks gestation.
- To evaluate risk factor strategies and swab types (vaginal alone vs. combined vaginal/perianal) for GBS detection.
Main Methods:
- Women provided vaginal and perianal swabs at 31-33 weeks, 35-38 weeks, and during labor.
- Swabs were cultured using layered horse blood agar and selective broth.
- Test characteristics were calculated for different screening strategies and timings.
Main Results:
- A high-risk strategy was ineffective in predicting GBS status during labor.
- Delaying GBS screening until 36 weeks significantly improved the identification of colonized women.
- No clear advantage was found for combined vaginal and perianal swabs over vaginal swabs alone.
Conclusions:
- This study provides clear evidence for optimal GBS screening timing.
- Adding a perianal swab to vaginal swabs does not offer a significant benefit.
- Findings will aid communication between clinicians and pregnant women regarding GBS prevention.