OBSTERTRIC NURSING NUR-201/NUR-217/NUR-218 CONCEPTS IN CARE OF THE CLIENT IN OBSTERTRICS AND GYNECOLOGIC NURSING. COMPONENTS OF LABOR (4Ps of Labor)
A successful labor depends on four integrated concepts:
1. A woman’s pelvis (the passage) is of adequate size and contour.
2. The passenger (the fetus) is of appropriate size and in an advantageous position and
presentation.
3. The powers of labor (uterine factors) are adequate. (The powers of labor are strongly
influenced by the woman’s position during labor.)
4. A woman’s psychological outlook (psyche) is preserved, so that afterward labor can be viewed
as a positive experience.
Passage
The passage refers to the route a fetus must travel from the uterus through the cervix and
vagina to the external perineum. Because the cervix and vagina are contained inside the pelvis,
a fetus must also pass through the bony pelvic ring. Two pelvic measurements important to
determine the adequacy of the pelvic size: the diagonal conjugate (the anteroposterior
diameter of the inlet) and the transverse diameter of the outlet. At the pelvic inlet, the
anteroposterior diameter is the narrowest diameter; at the outlet, the transverse diameter is
the narrowest.
• Critical factors:
o Size of maternal pelvis (diameters of the pelvic inlet, midpelvis, and outlet)
o Type of maternal pelvis
▪ Gynecoid – best for delivery
▪ Android – mostly in males
▪ Anthropoid – for black women
▪ Platypelloid – Transverse position of the baby
o Ability of the cervix to dilate and efface
o Ability of the vaginal canal and the introitus (an entrance to descent) to distend.
Passenger
The passenger is the fetus. The body part of the fetus that has the widest diameter is the
head, so this is the part least likely to be able to pass through the pelvic ring. Whether a fetal
skull can pass depends on both its structure (bones, fontanelles, and suture lines) and its
alignment with the pelvis. Movement of the fetus through the birth canal is determined by
several interacting factors: fetal head, attitude, lie, presentation, and position.
• Fetal head – most important part of the fetus to be seen by OBs; largest part of the
fetus, most frequent presenting part, and least compressible of all parts
• The head is important in manipulating the baby:
o Has 7 bones: frontal (2), parietal (2), temporal (2), and occipital (1)