Labour Flashcards
Describe the borders of the pelvic inlet and outlet. Why is it important to know the anatomy of the pelvic inlet + outlet for understanding labour?
Inlet: sacral promontory, arcuate line of the ilium, pubic symphysis
Outlet: pubic arch, ischial spines, coccyx
*Baby’s head must enter the inlet in the transverse plane (the widest part) and then turn to exit the outlet in the AP plane
What is the clinical relevance of the ischial spines?
- Site of pudendal nerve -> nerve block for LA during instrumental delivery/episiotomy
- ‘Station 0’, used when describing the level of the head during delivery. Can only use instruments when at station 0 or lower
Describe the anatomy of the fetal skull. Why is this relevant for labour?
- Bones have not yet fused. The meeting points are the anterior and posterior fontanelles
- Anterior: diamond shape
- Posterior: triangle shape
- Can feel the baby’s head PV during labour to assess the presenting part + attitude (head position)
What is the ideal presentation, position + attitude of the fetus?
Vertex presentation, occipito-anterior position
Well-flexed fetal head (or hyperextended)
Describe the changes that occur in the cervix prior to labour, and the mechanism for these changes.
Cervix softens, dilates, shortens, and thins (effacement).
Prostaglandins induce proteolysis, which breaks down collagen and elastin -> softening
There is also an increase in hyaluronan, which brings water- this is ‘ripening’
Describe the changes that occur in the uterus prior to/during labour, and the mechanism.
- Uterus has rhythmic, regular, strong contractions
- Stimulated by oxytocin and prostaglandins -> increase intracellular Ca2+
- Also have progressive shortening of the muscle fibres in the upper segment -> squeezing baby out
What is the Fergusson reflex?
Oxytocin released in response to pressure on the cervix
How would you diagnose the onset of labour? What is NOT the onset of labour?
- Presence of strong, regular, painful contractions
- Progressive cervical changes (dilatation + effacement)
- Labour does not necessarily begin with the loss of the mucus plug (the ‘show’) or rupture of membranes, though these can precede labour
Define the stages of labour.
1st stage: from the onset of contractions to full dilatation (10cm).
-Divided into the latent phase- up to 3-4cm. and the active phase- up to 10cm.
2nd stage: From full dilatation to delivery of the baby.
-Divided into the passive phase- no urge to push. and active 2nd stage- reflex to bear down.
3rd stage: delivery of the placenta and membranes
How long is a normal labour? How long is each stage?
Normal 1st labour is about 8 hours, 2nd is 5 hours.
- 1st stage: latent 3-8 hours, active 2-6 hours
- 2nd stage: passive 1-2 hours, active 1-2 hours
- 3rd stage: several mins
What would be classified as prolonged labour?
Total: over 12 hours in nulliparous, 8 hours in multiparous women
- 1st stage: if not dilating 1cm/2hours
- 2nd stage: if 1+ hours in multiparous, 2+ hours in nulliparous
- 3rd stage: if >30 mins
Describe the mechanism of labour.
- Engagement: head enters the pelvic inlet
- Descent
- Flexion of the head
- Internal rotation (OA/OP)
- Extension
- Restitution (head aligns with shoulders automatically)
- External rotation (shoulders move into AP plane)
- Delivery of shoulders
- Delivery of body
How are contractions quantified?
Usually the number in 10 mins
eg. 2 in 10, 5 in 10
When should a woman contact the labour ward?
When contractions are =<5 mins apart, or when there is rupture of membranes
What happens when a woman comes to labour ward in labour?
Take a history:
-Labour: contractions (onset, timing, frequency), ROM (colour, amount), PV bleeding, fetal movements
-Current pregnancy, birth plan
-Obstetric history (number, mode of delivery, size)
-PMH
General exam: vitals, urine dip
Abdo exam: lie, presentation, engagement, contractions
Vaginal exam: palpate cervix (length, dilatation, effacement) and presenting part (position, station, attitude)
–> either decide if for midwifery care or obstetric care
How should labour be monitored?
In established labour: -Contractions every 30 mins -HR every 1 hour -BP, temp, PV exam every 4 hours In the 2nd stage: -HR, BP, temp, exam every hour
How should you monitor the fetus during labour when there are no identified issues?
Auscultate the fetal heartbeat using Pinnard or Doppler USS. x15 mins during 1st stage, x5 mins 2nd stage.
What are the methods of fetal monitoring? When would they be indicated?
- Auscultate fetal heart beat. Initial monitoring
- Cardiotocography (CTG)/External fetal monitoring. If abnormal FHR, maternal pyrexia, PV bleeding, lots of meconium, oxytocin used
- Fetal scalp elctrodes (FES). If CTG not possible eg. high maternal BMI
- Fetal blood sampling (FBS). If there is an abnormal CTG
What is a partogram? What does it show?
Visual representation of labour.
Shows cervical dilatation, frequency + strength of contractions, head descent, station, fluid, obs
-Can indicate if there is slow progression/delay
How would you manage a woman in the 1st stage of labour?
If in the latent stage: send home and tell to come back later. Use simple analgesia
If in the active stage:
-1:1 midwifery care
-Adequate pain relief, hydration
-Encourage mobility
-Monitor maternal obs, fetus, and progress
*Do not rupture membranes if progressing well
How would you manage a woman in the 2nd stage of labour?
- Encourage to stand/all 4s/squat
- Stop pushing when head crowns
- Protect the perineum, flex the fetal head
What immediate care does the baby need after delivery?
- Clamp and cut the cord
- Apgar scores at 1 min + 5mins
- Dry + warm
- Vitamin K injection
- Skin-to-skin
How would you manage the 3rd stage of labour?
- Active management is best to reduce PPH risk- oxytocin and ‘controlled cord traction’
- 10 IU oxytocin IM
- Clamp and cut the cord
- Pull on the cord during contraction + push fundus away
- Examine placenta to ensure no placental tissue remaining
- Inspect vulva for tears
Broadly speaking, what the main ways in which labour can be abnormal?
Labour can go wrong when there is poor progress or fetal compromise.
Can be due to the 3 P’s:
-Powers: eg. insufficient contractions
-Passage: pelvic inlet/outlet not big enough, cervical dystocia
-Passenger: baby too big/malpositioned
What are the 3 main patterns of abnormal progress in labour? What are the risk factors for each?
- Prolonged latent phase. RF- primiparous
- Primary arrest (poor progress in active 1st stage)/secondary arrest (>7cm then arrests)
- Inefficient contractions (dysfunctional uterine activity), CPD, malposition/presentation - Arrest in the 2nd stage
- Also malposition/presentation, CPD, pain, exhaustion
How would you manage poor progress in the 1st stage of labour?
-Assess the contractions. This is the likely cause of slow progress in the 1st stage of labour.
If primiparous:
-Amniotomy/artificial rupture of membranes (ARM)
-Oxytocin infusion (slowly, increasing every 30 mins until contractions 4-5 in 10 mins)
-If no progress with 4-6 hours of oxytocin, proceed with C-section
If multiparous: be careful. Oxytocin can lead to uterine rupture.
What is cephalopelvic disproportion? What are the risk factors? How would you manage it?
- The head is too large to pass through the pelvis.
- RFs: small mum, large head, primigravidae
- Management: can use oxytocin if only mild/mod degree in primiparous. Do not give to multiparous!!
What is the most important thing to bear in mind when giving a woman an oxytocin infusion?
If she is primiparous/multiparous.
Oxytocin infusion in multiparous women may cause uterine rupture if the labour is obstructed. So you want to be very sure that there really are inefficient contractions before giving oxytocin.
What are some causes of poor progress in the 2nd stage of labour?
- Secondary dysfunctional uterine activity due to epidural, ketosis, dehydration
- Deep transverse arrest (head stuck in narrow midpelvis)
How would you manage poor progress in the 2nd stage of labour?
- Amniotomy
- Consider oxytocin if secondary uterine dysfunction
- Instrumental delivery +/- episiotomy
- Consider if C-section more appropriate
When would you diagnose delay in the 2nd stage of labour?
- 2 hours and birth not imminent in primiparous
- 1 hour and birth not imminent in multiparous
How would you manage suspected fetal compromise on CTG?
- If suspicious CTG (1 feature abnormal): change position, give IV fluids, decrease/stop oxytocin (Syntocinon)
- If abnormal CTG (2+ features abnormal): vaginal exam, FBS. Consider need for C section/instrumental delivery
What forms of pain management can you use during labour?
Non-pharmacological pain management: breathing exercises, warm bath/shower
Pharmacological:
1. Opiates eg. pethidine, diamorphine IM/SC/PCA. But SEs include drowsiness, N+V
2. Inhalational: NO/Entonox
3. Epidural
4. Spinal block
Name the indications, contraindications, and complications of an epidural.
- Indications: patient’s choice, prolonged labour, hypertension, multiple pregnancy, likely C section
- Contraindications: coagulopathy, sepsis, hypovolaemia
- Complications: increased 2nd stage duration, increased instrumental delivery, dural puncture –> headache (1%), bladder dysfunction if not catheterised, hypotension, accidental total spinal anaesthesia
T/F. Hypertension is a contraindication to the use of epidural analgesia
False. Hypertension is an indication.
What is the most significant risk of labour in a woman with a previous C section? How would this present?
1/200 risk of dehiscence in spontaneous labour.
Uterine rupture would present with severe pain, PV bleeding, haematuria, absence of contractions, tachycardia.
This can progress to maternal shock and death, and fetal hypoxia + death.
How many women with previous C sections go on to have a VBAC?
70-80%. Others will have another C section.