Peggy Nygren, MA; Rongwei Fu, PhD; Michele Freeman, MPH; Christina Bougatsos, BS; Mark Klebanoff, MD, MPH; Jeanne-Marie Guise, MD, MPH
Acknowledgment: The authors thank Andrew Hamilton, MLS, MS, for conducting the literature searches, and USPSTF leads Kimberly Gregory, MD, MPH, Lucy Marion, PhD, RN, and Diana Petitti, MD, MPH, and AHRQ officers Iris Mabry, MD, MPH and Mary Barton, MD, MPP, for their guidance on this project.
Grant Support: This report was conducted by the Oregon Evidence-based Practice Center under contract to the Agency for Healthcare Research and Quality, Rockville, MD, according to Contract #290-02-0024, Task Order Number 2 for the USPSTF.
Potential Financial Conflicts of Interest: None disclosed.
Requests for Single Reprints: Peggy Nygren, MA, Oregon Health & Science University, Mail Code BICC, 3181 SW Sam Jackson Park Road, Portland, OR 97239; e-mail, firstname.lastname@example.org.
Current Author Addresses: Ms. Nygren, Drs. Fu and Guise, Ms. Freeman, and Ms. Bougatsos: Oregon Health & Science University, 3181 SW Sam Jackson Road, Portland, OR 97239.
Dr. Klebanoff: National Institute of Child Health and Human Development, National Institutes of Health, 6100 Executive Boulevard, Room 7B05F, MSC 7510, Bethesda, MD 20892.
Bacterial vaginosis is the most common lower genital tract syndrome among women of reproductive age. There has been continued debate about the value of screening and treating asymptomatic pregnant women for bacterial vaginosis.
To examine new evidence on the benefits and harms of screening and treating bacterial vaginosis in asymptomatic pregnant women.
English-language studies on Ovid MEDLINE (2000 to September 2007) and Cochrane Library databases (through September 2007), reference lists, and expert suggestions.
Screening, treatment, or adverse effect studies with pregnancy outcome data in women who are asymptomatic for bacterial vaginosis.
Study and patient characteristics, treatment variables, adverse pregnancy outcomes, and internal validity quality criteria from the U.S. Preventive Services Task Force (USPSTF) and Jadad scale were abstracted.
7 new randomized, controlled treatment trials and 2001 report data were combined in a series of meta-analyses to estimate the pooled effect of treatment on preterm delivery (<37, <34, and <32 weeks); low birthweight; and preterm, premature rupture of membranes.
No screening studies that compared a screened population with a nonscreened population were found. Significant heterogeneity was found among the high-risk treatment trials (P < 0.001). It is not clear from the detailed description of the studies which factors explain the differences in preterm delivery rates and potentially the association of treatment effect; however, both raise concern for the unintended potential for harm.
No benefit was found in treating women with low- or average-risk pregnancies for asymptomatic bacterial vaginosis. More research is needed to better understand these groups and the conditions under which treatment can be harmful or helpful, and to explore the relevance of bacterial vaginosis to other adverse pregnancy outcomes, such as delivery before 34 weeks.
Analytic framework and key questions.
KQ = key question.
Appendix Table 1. Overall Searches
Appendix Table 2. Specific Searches per Key Question*
Appendix Table 3. U.S. Preventive Services Task Force Quality Rating Criteria
Appendix Table 4. Jadad Scale Criteria
Appendix Table 5. Jadad Score Calculation
Search and selection of literature for all key questions.
BV = bacterial vaginosis; RCT = randomized, controlled trial. *Cochrane databases include the Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Database of Abstracts of Reviews of Effects. †Other sources include reference lists and expert suggestions. ‡We included 7 additional studies for key question 2 and 2 for key question 3 from the 2001 report in the summary of this evidence.
Study characteristics and absolute risk reduction of delivery before 37 weeks.
Span = treatment timing spans less than 20 weeks and greater than 20 weeks. *Baseline risk is the percentage of deliveries before 37 weeks in the placebo group. Absolute risk reduction is the difference in probability of delivery before 37 weeks (control minus treatment). †McDonald et al. (58) and Carey et al. (57) performed a high-risk group subanalysis; high-risk group is included in total study population of the average-risk target group. Odendaal et al. (50) included 2 target populations; high-risk and low-risk groups are 2 separate groups.
Absolute risk reduction of delivery before 34 weeks and before 32 weeks.
PTD = preterm delivery. *McDonald et al. (58) and Carey et al. (57) performed a high-risk group subanalysis; high-risk group is included in total study population of the average-risk target group. Odendaal et al. (50) included 2 target populations; high-risk and low-risk groups are 2 separate groups.
Absolute risk reduction of low birthweight and preterm, premature rupture of membranes (PPROM).
*McDonald et al. (58) and Carey et al. (57) performed a high-risk group subanalysis; high-risk group is included in total study population of the average-risk target group.
Table 1. Characteristics of Studies of Women at High Risk for Delivery before 37 Weeks*
Table 2. Outcomes Table: Benefits and Harms of Screening 1000 Pregnant Women at High Risk for Bacterial Vaginosis*
Illustration of calculation in Table 2, using the outcome of delivery before 34 weeks in the more selective high-risk group.
BV = bacterial vaginosis; PTD = preterm delivery. *To calculate the confidence limits for the increase or decrease in adverse outcome, plug in the confidence limits of effect size here. †A negative sign (−) indicates a net increase in adverse outcomes (harm), and a positive sign (+) indicates a net decrease in adverse outcomes (benefit).
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Nygren P, Fu R, Freeman M, Bougatsos C, Klebanoff M, Guise J. Evidence on the Benefits and Harms of Screening and Treating Pregnant Women Who Are Asymptomatic for Bacterial Vaginosis: An Update Review for the U.S. Preventive Services Task Force. Ann Intern Med. ;148:220–233. doi: 10.7326/0003-4819-148-3-200802050-00008
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Published: Ann Intern Med. 2008;148(3):220-233.
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