Primary versus secondary outcomes in gargantuan studies.

摘要

Epidural analgesia is currently the most effective method available to treat pain in labor. Retrospective studies conducted during the 1980s and 1990s suggested that epidural analgesia might slow the progress of labor and cause unnecessary Cesarean sections. Unfortunately, retrospective study cannot readily separate cause and effect. If patients with slower labor are more likely to receive epidural anesthesia, then a retrospective study may identify an association between epidural anesthesia and slowed labor, but it does not establish a causal link.