The normal mechanism of labour involves the fetus descending through the birth canal in stages. First, there is descent, flexion, and internal rotation of the fetal head as it engages in the pelvis. Next, further descent causes crowning and extension to deliver the head. The head then undergoes restitution and external rotation to align with the shoulders. Finally, the shoulders and body are delivered to complete the birth.

1. Normal Mechanism of Labour
SALSO COURSE
SARAWAK GENERAL HOSPITAL

2. Normal delivery

3. Pelvic inlet
Pelvic outlet

4. Definition
 Mechanism of labour - the series of
changes in position and attitude which the
fetus undergoes during its passage through
the birth canal

5. Normal mechanism of labour
Descent
Flexion
Internal rotation
Extension
Restitution
External rotation
Delivery of body
(DFI ERE)

6. Descent, flexion & internal rotation
•Descent continues and occiput reaches pelvic floor
•There is flexion of the head
•Occiput now rotates to the front
•Head is now in occiput-anterior
•This is internal rotation

7. Crowning
•Occiput is now below symphysis pubis
•Further descent pushes the head forward with
a movement of extension and the occiput is
delivered

8. Extension - delivery of head
•Increasing extension around symphysis
pubis delivers the bregma, brow and face

9. Restitution
•Head rotates to natural position relative to the
shoulders
•This is restitution

10. External rotation
•Further descent and rotation causes the head to rotate so that the
occiput lies to the left maternal thigh
•This is external rotation
•The anterior shoulder now slips under the symphysis pubis and
with lateral flexion of the fetal body, the posterior shoulder is born
•The rest of the body follows easily