This investigation of future research needs builds on the Comparative Effectiveness Review (CER) Strategies To Reduce Cesarean Birth in Low-Risk Women, conducted by the Vanderbilt Evidence-based Practice Center (EPC). The rationale for the review is a concerning increase in cesarean use over the past decade. Thirty-two percent of pregnancies in the United States conclude with a cesarean birth. This record high rate reflects a relative increase of 53 percent in use of cesarean from 1991 to 2007. The pattern of increasing use of cesarean has been of concern for decades, with the last decline of 2 to 3 percent, occurring in the mid-1990s, being fully reversed by 1999, and the rate increasing more than 50 percent from 1996 to 2007. Nearly one in three births by cesarean translates to a total of 1.4 million cesarean births each year, making cesarean the most commonly performed major surgery in the United States. Research has addressed predictors of cesarean such as the shift toward older maternal age, higher body mass index, greater maternal comorbidity, use of assisted reproductive technology, and increased incidence of multiple gestations. Nonetheless, relatively little focus has been placed on research specifically designed to assess strategies to reduce use of cesarean. The CER aimed to bring that literature to the forefront by systematically examining the outcomes of interventions intended to reduce use of cesarean among low-risk women. The Comparative Effectiveness Review addressed the following Key Questions (KQs): KQ1. What strategies during pregnancy are effective to reduce the use of cesarean birth among women with a singleton pregnancy who are intending a vaginal birth? KQ2. What strategies during labor are effective to reduce the use of cesarean birth among women with a singleton pregnancy who are intending a vaginal birth? KQ3. Where head-to-head comparisons are available, what strategies are shown to be superior in reducing the use of cesarean birth among women with a singleton pregnancy who are intending a vaginal birth? KQ4. What are the nature and frequency of adverse effects resulting from strategies used to reduce cesarean birth among women with a singleton pregnancy who are intending a vaginal birth? After reviewing the evidence, the EPC investigators concluded that, while some strategies show promise, no particular strategy was uniformly successful in reducing cesareans. The strength of the evidence was low to insufficient for each of the strategies reviewed. The CER noted topic-related evidence gaps in the literature and common methodologic issues. These gaps are summarized and categorized by the most relevant PICOTS (population, intervention, comparator, outcome, timing, and setting) elements. Two of the eight topic-related evidence gaps do not fit within the PICOTS framework and are described as "determinants." These gaps relate to macrolevel factors that influence patient, provider, and system preferences about cesarean and decisions to use cesarean.