Final answer:
The "four Ps" in obstetrics are Powers, Passage, Position, and Passenger. They refer to the contractions, birth canal and pelvis, baby's orientation and position, and the baby itself, respectively. Psyche is sometimes added to address the mother's psychological state during childbirth.
Step-by-step explanation:
The "four Ps" that a nurse must understand when practicing in the field of obstetrics include: Powers, Passage, Position, and Passenger.
Additionally, some resources include Psyche as a fifth 'P' to address the psychological aspects of childbirth.
The 'Powers' refer to the contractions that help to push the baby out during childbirth. 'Passage' involves the birth canal and pelvis that the baby must pass through.
'Position' relates to the baby's orientation and position within the uterus, which can affect the ease of birth. 'Passenger' stands for the fetus or baby that is being birthed. 'Psyche' addresses the mental state of the mother, which can impact labor and the childbirth experience.
Detailed explanations of these concepts can be found in obstetric nursing textbooks, where they explain the physiological and psychological adaptations in pregnancy, the stages of labor, and the postpartum period.