Agency for Healthcare Research and Quality (AHRQ) Evidence Report
The Oregon Evidence-based Practice Center (EPC) review was restricted to studies published between the 1980 National Institutes of Health (NIH) Consensus Development Conference on Cesarean Childbirth and March 2002. Databases searched included MEDLINE, HealthSTAR, Cochrane systematic reviews and controlled trials registries, Database of Abstracts of Reviews of Effects, National Centre for Reviews and Dissemination, and Excerpta Medica database databases. Search strategies are presented as appendices in the full evidence report. In all, 15,370 citations were retrieved.
Studies were included for review if they identified a group of patients with prior cesarean. Studies were excluded if they focused on the following: nulliparous patients, vertical, lower-vertical, classical or classic cesarean incision, an inability to differentiate outcomes based upon scar type, vaginal breech delivery, preterm delivery, multifetal pregnancy, or low birth weight, and for patients with particular conditions such as gestational diabetes, human immunodeficiency virus (HIV), and preeclampsia. Studies conducted in undeveloped or developing countries were excluded as were case reports, editorials, letters, and non-English-language papers.
Internal validity of individual studies was assessed using the United States Preventive Services Task Force (USPSTF) criteria, and were modified for some specific key questions. Large population-based and prospective cohort studies were included because randomized controlled trials (RCTs) of delivery method have not been done.
Updated Evidence Review
Because two years had passed since the original evidence review, the Trial of Labor After Cesarean (TOLAC) Panel conducted a systematic update of the evidence by reviewing studies published since the AHRQ evidence report. The update followed the same procedure as the AHRQ evidence report, used the same search strategies, and retrieved the abstracts of all English-language publications through March 2004. Studies were identified by search category as defined in Table 2 of the original guideline document and were read by two reviewers who applied the same inclusion and exclusion criteria defined in the initial report, and assigned remaining studies to the appropriate key question(s). Studies selected for full review were retrieved and evaluated for study quality using the same criteria as that of the initial report.
The results of the full review by key question are presented in Table 3 of the original guideline document. The updated search yielded only seven studies that received a fair to good rating. Only key questions 1 and 8 identified more than one study (three each). The new studies for key questions 1 and 8 did not address identical outcomes or have the same study focus. Accordingly, without a body of new evidence for any key question, the TOLAC Panel determined that there was no support for any substantive change to the original report. Therefore, the original evidence report was used as the evidence source for this guideline.