Stages of Labour

Stages of Labour

• 1st stage
• 2nd stage
• 3rd stage

Definitions of Stages

• 1st stage: Cervix

  • Begins with: diagnosis of labour.
  • Ends with: full dilatation of the cervix (0‑6 cm in the latent phase, 10 cm when fully dilated).Z

• 2nd stage: Baby

  • Begins with: full cervical dilatation.
  • Ends with: birth of the baby.

• 3rd stage: Placenta

  • Begins with: birth of the baby.
  • Ends with: delivery of the placenta.

Labour Overview

Stages of Labour

1st Stage

from the diagnosis of labour to full dilatation of the cervix (10 cm).

• It can be divided into two phases:
  • Latent phase.
  • Active phase.

Latent Phase

Begins with the onset of labour and ends when cx is 3–4 cm & ‘fully effaced’.

What is Effacement?

Shortening in length of cx, to becomes incorporated into the lower segment of the uterus.

Active Phase

Begins from cx dilatation from 3-4 cms dilatation & ends with fully dilatation(10cms).

2nd Stage

from full dilatation of the cervix to delivery of the fetus or foetuses.

Mechanism of Labour from full dilatation of the cervix to delivery of the fetus or foetuses. During the 1st & 2nd stages the following occur (mechanism of labour):

1. Engagement.
2. Descent.
3. Flexion.
4. Rotation.
5. Extension.
6. Restitution.
7. Delivery of the shoulders & rest of the baby.

3rd Stage

Interval between delivery of the baby & delivery of the placenta & membranes. (usually lasting 30 minutes).

i. Engagement

when the widest part of the presenting part passed through the pelvic inlet.

• Fetal head enters the pelvis in the transverse position.
• In nulliparous …usually by 37 weeks’ gestation.
• In multiparous women …may be delay till labour onset..
• Number of fifths :

Fetal head palpable abdominally. If more than two-fifths of the fetal head is palpable head is not engaged.

ii. Descent

During the first stage and second stage of labour descent of the fetus.

Why? As a result of uterine contractions.

In the second stage of labour, it is assisted by voluntary efforts of the mother using her abdominal muscles and Valsalva manoeuvre (‘pushing’).

iii. Flexion

The fetal head is not always completely flexed when it enters the pelvis.

As the head descends into the midpelvis ⇒ flexion occurs.

This occurs due to the surrounding structures and is important

Why? To reduce the presenting diameter of the Fetal head.

iv. Internal Rotation

• o If the head is well flexed ⇨ the occiput will be the leading point
• o When reaching the gutter of the levator ani muscle
  • ⇨ it will rotate anteriorly
    • ⇨ so the sagittal suture
  • lies in the APdiameter of the pelvic outlet
    • (i.e. the widest diameter).

v. Extension

• Following internal rotation …occiput is beneath the symphysis pubis.
• The well-flexed head now extends
• And the occiput escapes from underneath the symphysis pubis and distends the vulva.*
• This is known as ‘crowning’ of the head

vi. Restitution

• After crosses the perineum
• The head aligns itself with the shoulders… (which entered the pelvis in oblique position).
• This slight rotation of the occiput through one eighth of the circle is called: Restitution

vii. External Rotation

• Shoulders have to rotate into the direct AP plane
  • …In aim to be delivered.
  • (remember, the widest diameter at the outlet).
• When this occurs…
  • the occiput rotates through a further
  • one-eighth of a circle to the transverse position.
• This is called:
  • External rotation.

viii. Delivery of the Shoulders and Fetus

• After restitution and external rotation
  • …the shoulders will be in the AP position.
• The anterior shoulder :
  • is under the symphysis pubis… and delivers first.
• Then posterior shoulder delivers.
• This process occurs without assistance,
  • (Just gentle traction in a downward direction
  • to release the ant. shoulder from beneath the pubic symphysis.

• Normally the rest of the fetal body is delivered easily

Mechanism of Labour (Summary View)

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