The "push" for evidence: management of the second stage.

Recognition that the available evidence does not support arbitrary time limits for the second stage of labor has led to reconsideration of the influence of maternal bearing down efforts on fetal/newborn status as well as on maternal pelvic structural integrity. The evidence that the duration of 'active' pushing is associated with fetal acidosis and denervation injury to maternal perineal musculature has contributed to the delineation of at least two phases during second stage, an early phase of continued fetal descent, and a phase of "active" pushing. The basis for the recommendation that the early phase of passive descent be prolonged and the phase of active pushing shortened by strategies to achieve effective, but non-detrimental pushing efforts is reviewed. The rational includes an emphasis on the obstetric factors that are optimal for birth and conducive to efficient maternal bearing down. Explicit assessment of these obstetric factors and observation of maternal behavior, particularly evidence of an involuntary urge to push, should be coupled with the use of maternal positions that will promote fetal descent as well as reduce maternal pain. The use of epidural analgesia for pain relief can also be accompanied by these same principles, although further research is needed to verify the strategies of "delayed pushing" and maintenance of pain relief along with a reconceptualization of the second stage of labor.