Strengths and Limitations
To our knowledge, this is the first systematic review to identify key
outcomes reported in studies evaluating planned mode of birth. The
strengths of the present study include its comprehensive search strategy
and methodological design following methodology of previous publications
in this field 12, 23. To prevent bias in the review
process, study selection was conducted independently by two researchers
and discrepancies were resolved through discussion. However, the
exclusion of retrospective studies and strict inclusion criteria meant
that certain useful reported outcomes may have been omitted. Whilst it
may be useful to review retrospective trials, the outcome selections in
retrospective trials could be influenced by many factors, including
finances and time frame, and tend to have reporting bias, therefore
affecting the quality of outcomes and outcome measures selected. The
high prevalence of reporting bias could have an impact on the
conclusions in Cochrane reviews 24. Given that up to
85% of studies are wasted throughout various stages of research,
accumulating a loss of tens of billions of dollars of investment in
research annually, improved methodological input for research design at
an early stage, such as selecting appropriate outcomes, is detrimental25.