Final answer:
Labor progression is affected by the passageway, the passenger (fetus), and psychosocial factors; these elements impact how labor starts, progresses, and ultimately culminates in delivery.
Step-by-step explanation:
The critical factors affecting the progress of labor include the passageway (birth canal), the passenger (fetus), and psychosocial factors. The passageway refers to the mother's pelvis and birth canal. The passenger pertains to the fetus and includes factors such as the size, position, and presentation. Psychosocial factors encompass the mother's emotions, anxiety levels, and support system which can influence labor progress. Other factors occasionally considered but not typically as critical include productivity (efficiency of contractions), which is sometimes alluded to in the discussion of Pitocin administration to stimulate labor. It's important to note that while productivity does contribute to the labor process, it is more of an intervention to enhance the natural labor process rather than a primary factor that affects it from the outset.