Mechanism of labour are the collective series of movements which the foetus has to undergo in order to pass through the birth canal.
1. ENGAGEMENT
This is a medical term often referred to as “baby dropping.” This means that the foetal head have settled into the pelvis prior to labor. If this is your first pregnancy( primigravida), engagement will usually occur about two or three weeks prior to the onset of labor. While in multigravida engagement takes place in labor.
**2. DESCENT: **
This is when your baby's head moves down (descends) further through your pelvis. Most often, descent occurs during labor, either as the cervix dilates or after you begin pushing.
**3. FLEXION: **
The uterine contractions will help the baby to descend and flex to present with the smallest diameters. So as the vertex descends into the maternal pelvis, it will encounter resistance from the maternal pelvic floor muscles. This will cause the flexion of the foetal head onto the thorax.
**4. INTERNAL ROTATION OF THE HEAD: **
As the presenting part meets the resistance of the pelvic floor muscle, it will rotate forward to lie under the SYMPHYSIS PUBIS. This is the turning forward of the fetal head to face the back of the mother as it reaches pelvic floor muscles. This causes a twist in the neck of the foetus.
5. CROWNING
As the presenting part distend the perineum,it will no longer descend back. This is when the baby's head start to be seen or emerge bit by bit during each contraction.
6. EXTENSION OF THE HEAD
This is the movement by which flexion is undone. Here, the face and chin passes over the thined out perineum and sweeps the perineum and the baby will give you a smile"hello!"
7. RESTITUTION
is the turning of the head to undo the twist in the neck that resulted from internal rotation remember...
**8. Internal rotation of the shoulder and external rotation of the head: **
Happens at the same time and in the same direction. The shoulder will enter the pelvic brim in the left oblique direction while the head will also follow in that same direction.N
The anterior shoulders meets the pelvic floor muscles first and will rotate forward to lie under the symphysis pubis.
9. BIRTH OF THE SHOULDERS
The Anterior shoulder will escape under the pubic arch and be born by downward traction while the posterior shoulder will sweep the perineum and be born by upward traction.
10. LATERAL FLEXION:
The rest of the body is then expelled simultaneously over the mother's abdomen by lateral flexion.
