Stages of Labour & Normal Delivery

Original article by Tom Leach | Last updated on 4/4/2015
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What is a ‘normal delivery’?

Normal time of delivery is between 38 and 41 weeks since the LMP (which is between 36 and 39 weeks gestation)
Approx 70% of all babies are born at this gestation, and 80% within 1 month of the predicted date
Occurs with 24h of the onset of regular contractions. This period is often preceded by a show – involving expulsion of the cervical mucus plug and a small amount of blood. Often also accompanied by ROM (rupture of membranes).
Method of delivery

  • About 60% of deliveries are without medical intervention.
  • In a further 20% it is thought that medical intervention is unnecessary
 

Braxton-hicks contractions

From the 1st trimester, the uterus undergoes physiological contractions (‘practice contractions’). These increase the pressure in the uterus to about 15mmHg. They become particularly common after week 36.
  • During normal labour, the contractions increase the pressure up to 60mmHg
 

The process of delivery (Labour)

This can be divided into three periods:
  • The first stage of delivery - Dilatation period, made up of the Latent stage (up to 4cm), the active phase (up to 10cm
  • The second stage of delivery - Expulsion period
  • The third stage of delivery - After birth period
 

The first stage of delivery

This is the time between the onset of regulation contractions, and full dilatation of the cervix. Before dilatation begins, the shape of the cervix changes. In normal pregnancy, there is a ‘bulb’ shaped cervix. At delivery, the bulb flattens. This is known as effacement. Officially, according to the WHO. This stage begins when there are regular contracts and the cervix has fully effaced, and dilated to at least 3cm.

Rate of dilatation – a normal rate is 1-3cm / hour
Time to achieve full dilatation - varies greatly, but is generally shorter the higher the number of previous pregnancies. E.g. 12h primip, 7h multip.
Monitoring – during this period you should check:

  • Vaginal examination – every 4 hours. Asses dilatation and position of the head (measured in cm above the ischial spine)
  • Maternal urine every 4 hours for ketones and protein
    • If ketones present – give the mother 10% dextrose IV
  • Maternal BP and temp every ½ hour
  • Contractions every 15 min
    • Strength – during a contraction, you shouldn’t be able to indent the uterus with your fingers
    • Duration – usually 3 or 4 per 10 mins, lasting <1 min each
  • Fetal HR – every 15 min
    • Particularly measure just before and just after each contraction

Consider – LAPPED

  • Lie – e.g. longitundinal, transverse
  • Attitude – i.e. posture, flexed or extended
  • Presentation – e.g. cephalic, breech
  • Position – e.g. left occipto anterior
  • Engaging diameter
  • Denominator – the presenting part, e.g. in cephalic presentation, it is the occiput. Could also be face, brow etc
 

The second stage of delivery

Occurs between complete dilatation until the baby is born
  • Complete dilatation is 10cm
The mother will feel the urge to push, and will do so using the abdominal muscles, and the valsalva After delivery manoeuvre (exhaling against a closed airway to increase intra-thoracic pressure).

Normal duration of the second stage of labour:

  • 45 – 120 min in a primip.
  • 15-45 min in a multip
  • Delaying clamping the cord for 30 seconds, and also holding the baby 20cm below the level of the mother for this period helps to increase hematocrit (and thus reduce need for transfusion) in premature babies
 

Delivery of the baby from left occipto anterior presentation

Engagement

  • This is said to have occurred once the largest part of the fetal head has entered the pelvis. Station is a term used to describe the descent of the head. The station is “0” when the head is at the level of the ischial spines. Negative numbers describe (in cm) how far above the ischial spines the head is. Positive numbers indicate (in cm) how far below the ischial spines the head is.

Descent and flexion of the head

  • Imagine the pelvic floor muscles are like a gutter, running anterior to posterior.
  • As the baby’s head reaches the pelvic floor, it tries to line up with the ‘gutter’. So it turns (roughly 45 degrees) so that the face is pointing posteriorly. The shoulders remain in the left occipito anterior position (oblique)
  • The head then crowns (becomes visible), and is delivered. The head will extend (I remember it as trying to look away from the mum’s bum!).

Restitution

  • The head then re-aligns with the shoulders – turning back 45 degress to face postero-laterally. This is called restitution.

External rotation

  • Now, the shoulders reach the gutter of the pelvic floor, and they too line up with the gutter . The head will be seen to rotate45 degrees with the shoulders, so that it now lies transversly, looking at the mothers right leg. Thus the shoulders turn, so that the baby now lies in a transverse position (left shoulder anterior, right shoulder posterior).
  • Usually the anterior shoulder is delivered first, as the weight of the head pulls it down and out. Then the posterior shoulder is delivered.
  • The rest of the baby should follow soon after.
 
The video below is a reasonable representation, however there are a couple of things that might not be completely accurate / are slightly different to the description above:
  • The presentation in the video is more left occipito transverse than left occipito anterior
  • The shoulders in the video rotate with the head both before and at restitution. In reality, restitution is when the shoulders and the head re-align into the left-occipto anterior position.
 

The third stage of delivery

This is the delivery of the placenta, and membranes, and the control of bleeding. After delivery of the baby, the uterus will quickly shrink down to about the size it is at 24 weeks. Then the placenta will separate from the uterine wall, and there is usually some blood loss from behind the placenta.
  • The third stage usually only lasts a few minutes.
  • Routinely, syntometrine is given (ergometrine maleat + oxytocin). This reduces the third stage time to <5mins, (usually around 30 minutes) and reduces the risk of post partum haemorrhage. CI’s: pre-eclampsia, hypertension, liver / renal impairment, severe heart disease, familial hypercholesterolaemia. If BP is unknown, give oxytocin alone.

 

Post-partum haemorrhage

This is the loss of >500ml blood after delivery (or >1000ml after c-section). It is a major cause of MATERNAL MORBIDITY. Cause of PPH are the four T’s:

  • Trauma – trauma from the delivery
  • Tissue – retention of the placenta
  • Thrombin – refers to coagulation disorders
  • Tone: uterine atony – loss of tone of the uterus. Normally, the tone of the uterus compresses the blood vessles within it, and reduces blood flow. This helps to prevent bleeding.

Up to 80% of PPH are due to uterine atony
RF’s for atony:

  • Polyhydramnios
  • Multiple gestations
  • Prolonged labour
  • Excess oxytocin

Syntometrine should only be given after the head and anterior shoulder have been delivered! Otherwise, it can cause shoulder dystocia. When it is given, this is known as active management of the third stage.
Check all of the placenta has been delivered – leaving any behind can lead to infection, and cause PPH.

 

Finishing off

Consider prophylaxis for DVTConsider when:
  • Age >35, PLUS
  • BMI >35 or weight >90Kg, PLUS
  • Any other RF (see box)
    • OR
  • Any two RF’s (see box)
    • Well’s score not really relevant

 

Prophylaxis:

  • LMWH as soon as delivered (e.g. enoxaparin)
  • Confirm no PPH
  • Wait >4hr after epidural insertion or removal (>6h if traumatic)
  • Continue for 3-5 days – even at home
  • TED stockings – Transverse elastic graduated stockings
RF’s for DVT after deliver