Which factor significantly affects labor progression?

The supportive presence of a doula or partner significantly affects labor progression by providing emotional support, encouragement, and physical comfort to the birthing person. Research shows that continuous support during labor can lead to shorter labor durations, reduced need for interventions, lower rates of cesarean sections, and improved overall experience for the birthing person. The presence of a supportive individual can help create a positive and calming environment, which can ease anxiety and enhance the body's natural ability to labor effectively.

Other factors listed, such as time alone during labor, while possibly beneficial for some individuals, often do not contribute to improved outcomes like the presence of a supportive person does. The type of bed used for labor and the comfort of clothing are also aspects that may contribute to the comfort of the birthing individual but do not have the same profound impact on the progression of labor as the emotional and physical support provided by a doula or partner.