Normal Labour

Labour is a physiological process during which the fetus, membranes, umbilical cord and placenta are expelled from the uterus

Physiology

Initiation of labour

• Change in estrogen/progesterone ratio

• Fetal adrenals and pituitary hormones may control timing of the onset of labour

• Myometrial stretch increases excitability of myometrial fibres

• Mechanical stretch of cervix and fetal of membranes

• Ferguson's reflex

• Progesterone keeps the uterus settled - prevents formation of gap junctions, hinders the contractibility of myocytes

• Estrogen makes the uterus contract and promotes prostaglandin production

• Oxytocin initiates and sustains contraction, acts on decidual tissue to promote prostaglandin release
• Oxytocin is synthesized directly in decidual and extraembryonic fetal tissues, and in the placenta

• Pulmonary surfactant secreted into amniotic fluid has been reported to stimulate prostaglandin synthesis

• Increase in production of fetal cortisol stimulates an increase in maternal estriol

• Increase in myometrial oxytocin receptors and their activation results in phospholipase C activity and subsequent increase in cytosolitic calcium and uterine contractility

Cervical changes

• Cervical softening - increase in hyaluronic acid will decrease bridging among collagen fibres, decreasing firmness of the cervix

• Cervical ripening - changes include a decrease in collagen fibre alignment and strength, decrease in tensile strenght of the cervical matrix, and an increase in cervical decorin

Stages of labour

• Latent phase - mild irregular uterine contractions, cervix shortens and softens, duration variable
• May last a few days

• Active phase - 4cms onwards to full dilatation
• Slow decent of the presenting part
• Contractions progressviely become more rhythmic and stronger
• Normal progress is assessed at 1-2cms per hour

• Starts with complete dilatation of the cervix fully dilated (10cms) to delivery of the baby

• In nulliparous women it is considered prolonged if it exceeds 3 hours if there is regional analgesia, or 2 hours without

• In multiparous women it is considered prolonged if it exceeds 2 hours with regional analgesia or 1 hour without

• In low risk care vaginal examinations are not always carried out to assess time of full dilatation

• Delivery of the baby to expulsion of the placenta and fetal membranes

• ~10 mins

• After 1 hour, preparation made for surgical removal either by regional analgesia or under GA

• Expectant management - spontaneous delivery of the placenta

• Active management - use of oxytocic drugs and controlled cord traction is preferred for lowering risk of post partum haemorrhage

Contractions

• Uterine muscle - smooth muscle in connective tissue, density highest at the fundus

• Pacemaker - region of tubal ostia, wave spreads in a downward direction

• Synchronisation of contraction waves from both ostia

• Polarity: upper segment contracts and retracts, lower segment and cervic stretch, dilate and relax

• Normal contractions have a fundal dominance with a regular pattern and adequate 'resting tone'

Factors affecting passage of baby

• Types of pelvis
• Gynaecoid pelvis is the most suitable female pelvic shape

• Bony outlet of pelvis

• Cervical assessment - effacement, dilatation, firmness, position, level of presenting part or station

• Fetal position

7 cardinal movements of labour

1. Engagement - passage of the widest diameter of the presenting part to a level below the plane of the pelvic inlet

2. Descent - downward passage of the presenting part through the pelvis

3. Flexion - flexion of the fetal head occurs passively as the head descends due to the shape of the bony pelvis and resistance offered by the soft tissues

4. Internal rotation - rotation of the presenting part from its original position to the anterior position as it passes through the pelvis

5. Crowning and extension - occurs once the fetus has reached the level of the interoitus, bringing the base of the occiput in contact to the inferior margin at the symphysis pubis
1. Care of the perineum at birth is vital to reduce trauma
2. Delivery of head should be managed carefully and slowly with hands guiding but not leading the exit at crowing to prevent rapid extension of tissues and perineal tearing
3. Episiotomy may be required to prevent trauma to anal sphincters

6. Restitution and external rotation - the return of the fetal head to the correct anatomic position in relation to the fetal torso

7. Expulsion, anterior shoulder first - delivery of the rest of the fetal body

Puerperium

• Period of repair and recovery ~ 6 weeks involving return of tissues to non-pregnant state

• Bloodstained discharge lasts 10-14 days following birth

Clinical presentation

Braxton Hicks contractions

• 'False labour'

• Tightening of the uterine muscles, thought to aid the body to prepare for birth

• Can start 6 weeks into pregnancy but more usually felt in the third trimester

• Irregular, do not increase in frequency or intensity

• Resolve with ambulation or change in activity

• Relatively painless

True labour contractions

• Happen under the influence of the releas of oxytocin, which stimulates the uterus to contract

• True labour is when the timing of the contractions become evently spaced, and the time between them gets shorter and shorter

• Real contractions will get more intense and painful over time

Signs of the third stage

• Expulsion of placenta usually 5-10 minutes after delivery, considered normal up to 30 minutes

• Uterus contracts, hardens and rises

• Umbilical cord lengthens permanently

• Frequently a gush of blood variable in amount

• Placenta and membranes appear at introitus

Investigations

• Bishop's score is used to determine whether if it is safe to induce labour
• Position, consistency, effacement, dilation, station in pelvis

• Partogram: a graphic record of key data (maternal and fetal) contained onto one sheet, used to assess progress of labour i.e. cervical dilatation, fetal heart rate

Management

Analgesia in labour

• Non-pharmacological methods
• Exercise/movement
• Heat e.g. warm bath, heat pack
• TENs stimulation
• Acupuncture
• Hypnosis
• Massage

• Nitrous Oxide (Entonox or 'gas and air')

• Simple analgesia
• e.g. paracetamol

• Opiate analgesia
• Oral codeine phosphate
• IV/IM Diamorphine

• Epidural analgesia
• Does not impair uterine activity
• Associated with a longer second stage of labour
• Does not increase chance of caesarean birth but there is a slightly increased chance of an operative birth
• Complications: hypotension, dural puncture, headache, high block, atonic bladder

• Pudendal nerve block

Delayed cord clamping

• Immediate clamping of the umbilical cord can reduce the red blood cells an infant receives at birth by more than 50%, resulting in potential short‐term and long‐term neonatal problems

• With delayed cord clamping a higher red blood cell flow to vital organs in the first week was noted, and term infants had less anaemia at 2 months and increased duration of early breastfeedin

• Delayed clamping, should be carried out unless immediate resuscitation is necessary - from cessation of pulsations, or up to 3 minutes after expulsion

Skin to skin

• Early placing of the naked baby on the mother’s chest (SSC) helps keep babies warm and calm and considered to improve other aspects of a baby's transition to life outside the womb

Active management of third stage

• Includes prophylactic administration of syntometerine (ergometrine maleate and oxytocin) or oxytocin