Trials isolating a single intervention also prevent us from determining if elements of physiologic care work synergistically to produce better outcomes. Trials of spontaneous versus coached pushing typically require women in both arms to push on their backs. Conversely, trials comparing supine with nonsupine positioning use coached pushing in both arms. By deconstructing the package of physiologic care into its component parts, such trials cannot tell us how coached pushing on one’s back compares with spontaneous pushing in the position(s) of a woman’s choosing.

Passage from chapter 13, Second-Stage Labor: Lead, Follow, or Get out of the Way?