Labor is a physiologic process during which the fetus, membranes, umbilical cord and placenta are expelled from the uterus.

1. PRESENTED BY
MR KALYANKUMAR MSC(N)
Mechanism of Labour

2. Definition
 Series of events that occur on the head and the
fetal trunk in the process of adaptation, during
its journey through the pelvis.

3. Mechanism of labour
Engagement of head
Flexion of head
Internal rotation of head
Crowing
Extension and birth of head
Restitution
Internal rotation of shoulders & external rotation of head
Birth of shoulders & trunk by lateral flexion
(Descenttakesplacethroughoutbirthingprocess)

4. First stage of labour
 It starts from onset of labour pains to the full dilatation of
the cervix.
Latent phase:
 Cervix dilated to 0-3 cm
 Mild and short contractions
Active phase: Moderate to strong contractions
 Cervix dilates to 4-7 cm
 Bloody show
 Membranes may rupture

5. Transition phase: Strong contractions
 Cervix dilates 7-10 cm
 Increased bloody show
 Irritable, restless, emotional
 Leg tremors, sudden nausea and vomiting.
Duration: 12 hours in primigravida
 6 hours in multigravida.
 Duration of labour varies and influenced by :- Parity,
psychological state, presentation, position, pelvic shape.

6. Second stage of labour
 It starts from full dilatation of the cervix to the expulsion of
fetus from birth canal.
Latent phase: May last upto 1 hour
 Decrease in frequency and increase in strength of
contractions
Active phase: Urge to push
 Stronger and closer contractions

7. Transition phase: Begins with fetal head on perineum;
perineum bulges.
 Leg cramps are common.
Duration: Average duration is around one hour in
primigravida and 30 minutes in multigravida.

8. Third stage of labour
 In this stage, the separation and expulsion of placenta takes
place.
 After delivery some women have shivering, after short interval
discomfort in the lower abdomen reappears due to uterine
contractions
 Before separation of placenta, fundal height reaches below the
umbilicus and the uterus becomes discoid in shape
 After separation, placenta comes down into lower uterine
segment
The signs of placental separation are:
 Sudden gush of blood
 The length of the umbilical cord increases
Duration: Average duration is 5-15 minutes.

9. Fourth stage
 This is from expulsion of placenta until 2 hours after the
birth.
 This is an important period and requires close
observation of the mother. The mother is kept in the
delivery room for 1 hour. She is checked for bleeding, blood
pressure and pulse .

10. Summary
Conclusion