The Four P's of Labor Passageway
Passenger
Powers
Psyche
Passageway (The Four P's) The birth canal, including the mother's bony pelvis and soft tissues.
Passenger (The Four P's) The fetus and the placenta moving through the birth canal.
Powers (The Four P's) The physiological forces, including uterine contractions and maternal pushing
efforts.
Psyche (The Four P's) The mother's psychological state, emotional readiness, and coping response during
labor.
Components of the Passageway Bony pelvis, soft tissues of cervix, and vagina.
Parts of the true pelvis Pelvic inlet, midpelvis, and pelvic outlet.
False pelvis Shallow portion above pelvic brim that supports abdominal viscera.
Gynecoid Pelvis Normal female pelvis, transversely rounded. Most favorable for successful labor and
birth.
Anthropoid Pelvis Oval-shaped pelvis with an adequate outlet and narrow pubic arch.
Android Pelvis Heart-shaped male-like pelvis. Not favorable for labor; causes slow descent.
Platypelloid Pelvis Flat pelvis with oval inlet and short anteroposterior diameter. Difficult birth.
, Chapter 8 | Introduction to Maternity and Pediatric Nursing |
Obstetric conjugate Smallest front-to-back distance through which the fetal head must pass in the pelvic
inlet.
Full cervical dilation Equal to 10 cm, necessary along with complete effacement for birth.
Which pelvis type is most favorable for a vaginal birth? Gynecoid pelvis
Why is the fetal skull the most important fetal structure in It is the largest and least compressible part of the fetus.
labor and birth?
Molding (fetal skull) The overlap of skull bones to facilitate passage through the birth canal.
Fetal lie Position of long axis of fetus in relation to long axis of pregnant woman.
Longitudinal lie Fetal long axis is parallel to the maternal long axis.
Transverse lie Fetal long axis is perpendicular to the maternal long axis.
Oblique lie Fetal long axis is at an angle to the maternal long axis.
Fetal presentation The foremost part of the fetus that enters the pelvic inlet.
Three main fetal presentations Cephalic (head), breech (feet or buttocks), and shoulder (scapula)
Cephalic presentation Fetal presentation where the head enters the pelvic inlet first (majority of fetuses).