Normal Labour and Delivery

A pregnancy is term if it is after 37 weeks and before 42 weeks gestation.

Braxton-Hicks contractions

  • These are contractions that can start as early as the first trimester (usually start in the late 2nd trimester)
  • They are infrequent, irregular and involve mild cramping that lasts only a few minutes
  • Their function is thought to be to ‘prepare’ the body for labour- towards the end of pregnancy, they become more frequent, longer in duration and stronger

Towards the end of pregnancy there are other changes that increase the excitability of the uterus:

  • An increased progesterone:oetrogen ratio
    • progesterone inhibits contractility while oestrogen enhances and stimulates it
  • Oxytocin starts to be released, as do other foetal hormones e.g. oxytocin, adrenaline, prostaglandins
  • The mechanical stretch (caused by the large baby) increases the contractility of the uterus

Onset of Labour and the First stage of labour

Regular contractions start

  • Positive feedback loop
  • The first stage (dilation stage) of delivery can be defined as the time from the start of (semi)regular contractions to the full dilation of the cervix
    • NB the official definition (WHO) states that the first stage starts with regular contracts and the cervix dilated at 3cm (before this is technically not labour)
  • There are typically 2 phases of the 1st stage:
    • Latent phase- mild, more irregular contractions that shorten (efface) the cervix.  These become more intense and more regular with time.
    • Active phase- (true 1st stage)- starts around 3-4cm dilation: rapid cervical dilatation and foetal descent
      • This usually happens at about 1-3cm/hour, though will vary depending on parity (e.g. 12hr average for primiparous woman; 7hr average for multiparous woman)
  • Monitoring:
    • Assess dilatation and position of the foetal head
    • Check urine for ketones/protein (if ketones present consider administering 10% IV dextrose)
    • Check BP every half hour
    • Check contractions every 15 mins
      • Strength- palpation of the uterine fundus can give a rough estimate (the tenser/firmer, the stronger- you should not be able to indent the uterus with your fingers during a contraction)
      • Durations- usually 3-4 per 10 mins, lasting <1min each (however, this increases over the course of labour)
    • Foetal heart rate every 15 mins
      • Particularly with contractions  (SEE ALSO CTG)

Assessment of the baby’s lie

LAPPED

  • Lie- longitudinal/transverse/oblique
  • Attitude- posture (flexed/extended)
  • Presentation- Cephalic/breech
  • Position – e.g. Left Occipito Anterior
    • LOA is the most common position- the baby’s occiput is facing anteriorly and to the mother’s left (i.e. the baby’s back runs up the left side).  ROA is also common and rarely causes any problems.
    • LOP/ROP are not uncommon and may be able to be changed in utero by Leopold’s maneouvre (manual manipulation)
    • Face presentation/mental presentation will usually require caesarian.
  • Engaging diameter (width of foetal head)
  • Denominator – the presenting part (e.g. occiput)- this sort of comes under position too.

The Expulsion stage (second stage of labour)

Occurs from 10cm dilatation of the cervix until the baby is born.  The mother will feel the urge to push.  A normal 2nd stage will last:

  • 2 hours in a primiparous woman (3 hours if regional anaesthetic is used)
  • 1 hour in a multiparous woman (2 hours if regional anaesthesia is used)

There are 6 phases of the 2nd stage:

  1. Engagement
    1. See the image above.  ‘Station’ is the term used to describe engagement (+ve numbers are the number of cm below the ischial spines- 5cm is fully engaged)
    2. The baby’s head engages in a transverse position
  2. Descent and flexion of the head
  3. Internal Rotation of the head through 90° to face posteriorly (the shoulders remain in the LOA position i.e. 45° to head
  4. Delivery
    1. the baby’s head crowns in this position then delivers by extension of the head through the vaginal canal
  5. Restitution
    1. The head re-aligns with the shoulders (external rotation of 45°)
  6. External rotation
    1. The head and shoulders further externally rotate 45° (baby facing mum’s right leg) and the rest of the delivery will take place
    2. Usually the anterior shoulder is delivered first

NB A prolonged second stage is an emergency and requires caesarian section in most cases.

Third stage (Placental and membrane delivery)

  • Usually lasts a few minutes- syntocinon/ergometrine are often given to aid this process.
    • NB Ergometrine should not be given before the third stage as there is a risk of shoulder dystocia.  (Syntocinon is relatively safe and may be given to aid contractions in the first stage).

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