57. mechanism of labor

Question 1

what are the cardinal movements of labor?

Answer 1

changes in the fetal head position during it’s passage through the birth canal

1. Engagement
2. Descent
3. Flexion
4. internal rotation
5. Extension
6. External rotation/restitution
7. Expulsion

“Every Darn Fool In Egypt Eats Raw Eggs”

Question 2

what occurs during Engagement?

Answer 2

fetal presenting parts enter the pelvis

Question 3

what occurs during Descent?

Answer 3

head descends towards the pelvic floor

Question 4

what occurs during flexion?

Answer 4

occurs passively as the head descends due to the shape of the bony pelvis; this allows for the smallest diameter of the head to present to the pelvis

Question 5

what occurs during internal rotation?

Answer 5

the fetal head rotates so that the occiput turns anteriorly toward the symphysis pubis (assuming occiput anterior head position normally)

Question 6

what occurs during Extension?

Answer 6

the flexed head in the position continues to descend within the pelvis.
Because the vaginal outlet is directed upward and forward, extension must occur to allow the head to pass through it.

Question 7

what occurs during external rotation/ restitution?

Answer 7

as the head is delivered, with the release of the forces acting on it, it rotates back to its original position before internal rotation (the head aligns anatomically with the fetal torso).

Question 8

what occurs during Expulsion?

Answer 8

the anterior shoulder delivers under the symphysis pubis, followed by the posterior shoulder over the perineal body and the body of the newborn

Question 9

what is fetal station?

Answer 9

a measure of how far the fetus has descended in the pelvis.

Expressed as the number of centimeters of the leading bony edge of the presenting part above or below the level of the ischial spines; the maximum denominator is 5 (ex. 1 cm beyond the ischial spines corresponds to +1/5 cm).