Labour Flashcards
Define Labour.
Products of conception expelled from uterus >24 weeks gestation.
Before how many weeks gestation is labour considered pre-term?
Before 37 weeks
What is the average length of labour for primiparous and parous women?
primiparous - 10 hours (unlikely to exceed 18 hours)
parous - 5.5 hours (unlikely to exceed 12 hours)
Describe the 1st stage of labour.
Onset of regular contractions
Cervical changes
Lasts until full dilatation of cervix and no longer palpable
The 1st stage of labour is split into the early latent phase and the active phase. Describe the cervical changes that occur in each.
Early latent phase - cervix becomes effaced, shortens in length and dilates to 4cm
Active phase - cervix fully dilates to 10cm
Describe the 2nd stage of labour.
From full cervical dilatation to delivery of foetus
The 2nd stage of labour is split into passive and active stages. Describe each.
Passive - full dilatation of cervix prior to or in absence of involuntary expulsive contractions
Active - baby is visible/ persistent involuntary expulsive contractions/ other signs of full cervical dilatation/ active maternal effort in absence of involuntary expulsive contractions
When is prolonged 2nd stage abour diagnosed in nulliparious women?
At 2 hours
When is prolonged 2nd stage labour diagnosed in multiparious women?
At 1 hour
What is the first-line management of prolonged labour?
Refer to obstetric reg unless birth is imminent
List 4 complications of prolonged labour.
Foetal distress
PPH
Pelvic floor dysfunction
Fistulae
Describe the 3rd stage of labour.
Time between delivery of foetus and delivery of placenta and membranes
Occurs 10-15 mins post foetal delivery and can last up to 30 mins
Describe physiological management of the 3rd stage of labour.
No drugs, cord not clamped until pulsations ceased
Placenta delivered by maternal effort
Describe active management of the 3rd stage of labour.
Use of uterotonic drugs (oxytocin or syntometrine) with delivery of anterior shoulder or immediately after birth or before cord stops pulsating
Bladder catheterisation
Deferred cord clamping and cutting
Controlled cord traction after sings of placental separation
Outline the signs of placental separation from membranes.
The uterus contracts, hardens and rises
Umbilical cord lengthens permanently
There’s a gush of blood variable in amount
Placenta and membranes appears at introitus.
Outline the pros and cons of active management of the 3rd stage of labour.
Pro - shortens length of 3rd stage
cons - increase risk of N&V, haemorrhage and blood transfusion
When is a change from physiological management of 3rd stage labour to active management indicated?
Excessive bleeding of haemorrhage occurs
Failure to deliver the placenta within one hour
The patient’s desire to shorten the third stage.
Describe 3 clinical signs of the onset of labour.
Regular, painful contractions that increase in duration and frequency
Passage of blood stained mucous from cervix
Rupture of membranes
What is the definition of prelabour rupture of membranes?
If the period between rupture of membranes to painful contractions is >4hours.
Called premature rupture of membranes if occurs before full-term gestation.
Describe hormonal changes that occur to initiate labour.
progesterone decreases
oestrogen and oxytocin increase thus increasing prostaglandin production
CRH is also thought to be involved - increases oestrogen and prostaglandin synthesis and reduces progesterone
How does oxytocin act to initiate labour?
released from posterior pituitary
acts on decidual tissue to promote prostagladin release
Initiates and sustains contractions
Also synthesised directly in decidual and extraembryonic tissue and placental tissue
oxytocin receptors in myometrial and decidual tissues increases towards end of pregnancy to increase uterine contractility
State another 2 hormones that influence uterine myocytes.
relaxin
activin A
(influence cAMP production causing relaxation of myometrial cells. Relaxin also helps soften pelvic ligaments and the pubic symphysis so allow room for baby to exit)
Describe 3 changes in the cervix towards term gestation/in labour.
Decreased collagen
Increased hyaluronic acid (softens and stretches the cervix by decreasing affinity for fibronectin and collagen and increasing affinity for water)
Progressive uterine contractions causes effacement and dilatation of cervix
State the 7 stages of labour.
Engagement Descent Flexion Internal rotation Extension External rotation (restitution) Expulsion
How is engagement assessed in the 1st stage of labour.
Assessing how much of the foetal head can be felt in the abdomen, this is done in 5ths. i.e. if all of the head can be felt in the abdomen - it is 5/5 parts palpable. If no head can be felt it is 0/5 parts palpable.
List 8 possible causes of abnormal labour.
Malpresentation (non-vertex)
Malposition (occipitoposterior, occipitotrasnverse)
Preterm labour <37 weeks
Post-term labour >42 weeks
Too painful - requires anaesthestic input
Too quick (<2 hours) - hyperstimulation, precipitate labour
Too long - failure to progress
Foetal distress (hypoxia, sepsis)
Use the 3 Ps of labour to suggest reasons for failure to progress.
Powers - inadequate contractions
Passage - trauma, shape, cephalopelvic disproportion
Passenger - big baby, malposition
What are the possible complications of obstructed labour?
Sepsis - ascending genitourinary tract infection
PPH
fistula formation
Foetal asphyxia
Neonatal sepsis
Uterine rupture - increased risk if previous scar
Obstructed AKI
How is progression of labour assessed?
Vaginal examination every 4 hours to assess cervical dilatation, descent of presenting part and signs of obstruction (moulding, caput, anuria, haematuria, vulval oedema)
How is failure to progress defined?
<2cm cervical dilatation in 4 hours
State the 3 types of forceps that can be used for operative vaginal delivery and give an example of each.
Outlet forceps - Wrigley’s
Mid-cavity/ low-cavity forceps - Neville barnes, Andersons, Simpsons
Rotational forceps - Kielland’s forceps (should be performed with appropriate anaesthesia in theatre)
What is required for a forceps delivery?
HINT - use the pneumonic FORCEPS
Fully dilated cervix (10cm)
Occipitoanterior position (possible with Keilland forcepts and ventouse)
Ruptured membranes
Cephalic presentation
Engaged presenting part
Pain relief
Sphincter (bladder) empty - may require catheterisation
Give some indications for operative vaginal delivery.
Failure to progress in 2nd stage
Foetal distress
Maternal exhaustion
Special indication (i.e. if 2nd stage needs to shortened) include maternal cardiac disease, severe pre-eclampsia/ eclampsia, intra-partum haemorrhage, umbilical cord prolapse
List some disadvantages to operative vaginal delivery.
neonatal trauma; marks on babies face brachial plexus injury Facial nerve palsy Shoulder dystocia
Perineal trauma incl. 3rd and 4th degree tears Psychological trauma Bowel symptoms Urinary symptoms PPH
List some disadvantages to c-section.
Haemorrhage Infection VTE Visceral injury (bladder and ureters) Longer hospital stay Risk of uterine rupture in future labours x4 greater risk of maternal mortality Transient tachypnoea of the newborn
What are the advantages and disadvantages to ventouse delivery vs forceps?
less perineal trauma
more likely to fail
can cause cephalohaematoma and retinal haemorrhage
What are the contraindications to ventouse?
Prematurity (<34 weeks) Face presentation Suspected foetal bleeding disorder Foetal predisposition to fracture e.g. osteogenesis imperfecta Maternal HIV or hep C
Give 4 indications for the induction of labour.
>42 weeks gestation Pre-eclampsia Placental insufficiency and IUGR Antepartum haemorrhage Rhesus isoimmunisation Diabetes mellitus Chronic renal disease
What is used to assess the outcome of induction of labour?
Bishop’s score using cervical examination
What 5 measurements does Bishop’s score use?
Cervical dilatation (cm) Effacement (%) Station Cervical consistency Cervix position
score of 6 = labour likely after induction
score <5 = cervical ripening required
What determines the method of induction?
Whether membranes are ruptured
Bishop’s score
List the 5 methods of induction and give a caution for each.
Stripping of membranes/ sweep (involves finger inserted into cervix) - NNT high
Amniotomy to rupture membranes - requires soft cervix and engagement of head - risk of cord prolapse and placenta praevia
Synthetic oxytocin infusion (following amniotomy) - can cause uterine hyperstimulation leading to foetal asphyxia, may also cause uterine rupture
Cervical ripening and prostaglandin E2 (pessaries or gel applied to posterior fornix, or oral) - contraindicated if uterine scar due to risk of hyperstimluation or rupture
Mechanical cervical ripening - balloon catheter into cervix for 12 hours then removed to allow amniotomy
What measurements are involved in a partogram?
Foetal heart rate Cervical dilation Duration of labour Colour of liquor Frequency and duration of contractions Caput and moulding Station or descent of the head Maternal heart rate, BP and temperature
What is the common side effect of entonox gas?
nausea
What are the contraindications to regional anaesthesia during labour?
maternal refusal coagulopathy local or systemic infection uncorrected hypovolaemia inadequate staff experience or facilities
What are the 3 methods of regional anaesthesia during labour?
Epidural
Spinal
Pudendal nerve block
Give 3 advantages to epidural analgesia.
Complete pain relief in most women
Doesn’t increase risk of c-section
Can be controlled by patient
Can be topped up to allow operative deliveries
Give 3 disadvantages to epidural analgesia.
Lack of pressure sensation may reduce desire to push during active second stage
Reduced uterine contraction due to loss of Ferguson reflex
Increased risk of assisted vaginal delivery
Causes abnormal foetal heart rate
Hypotension
Accidental dural puncture
Postural headache dependent on gauge of cannula
High block may cause maternal respiratory depression
Atonic bladder
What does an epidural consist of?
Local anaesthetic agent (e.g. bupivacaine) injected into a fine catheter in the epidural space between L3-4
Addition of an opioid reduces dose requirement of bupivacaine and spares motor fibres to lower limbs and reduces complications i.e. hypotension and abnormal foetal heart rate
What is mechanism of action of a pudendal nerve block?
local anaesthesia injected around the pudendal nerve at the level of the ischial spine
often used for operative vaginal delivery
What are the disadvantages of pudendal nerve block?
can be ineffective
risk of haemorrhage from pudendal artery
risk of lignocaine toxicity if inadvertent muscular injection
How is spinal anaesthesia used?
catheter inserted into subarachnoid space between L3-4 and anaesthetic agent injected
commonly used for operative delivery
Why is spinal anaesthesia not used for pain control in labour?
because of the superior safety of an epidural and its ability to top up with suitable doses or use as a continuous infusion
Give some examples of narcotic analgesia that can be used in labour.
pethidine
morphine
remifentanil
What are the disadvatages to narcotic analgesia?
nausea and vomiting
foetal respiratory depression
What is the mechanism of action of remifentanil?
ultra-short acting opioid that offers superior pain relief to pethidine with less desirable SE on foetus
Give 3 maternal indications for CTG monitoring during labour.
Gestation <37 weeks or >42 weeks
Induced labour
Administration of oxytocin
Ante/intrapartum haemorrhage
Maternal illness (e.g. diabetes, cardiac or renal disease, hyperthyroidism, maternal infection)
Pre-eclampsia
Previous uterine scar (c-section or myomectomy)
Contractions > 5 in 10 or lasting more than 90 seconds
During/ following insertion of epidural block.
Maternal request
Give 3 foetal indications for CTG monitoring during labour.
Abnormal doppler artery velocimetry
Known or suspected IUGR
Oligohydramnios or polyhydramnios
Malpresentation
Meconium stained liquor
Multiple pregnancy (all babies need to be monitored)
Suspected small for gestational age or macrosomia
Reduced foetal movements in the last 24hours reported by the woman
Two vessel cord
Prolonged rupture of membranes >24hours unless delivery is imminent
A rise in baseline, repeated decelerations or slow to recover decelerations or overshoots.
Foetal structural abnormalities diagnosed during the antenatal period and planned for CEFM.
What may meconium indicate?
foetal distress/ hypoxia/ obstructed labour
prolonged pregnancy in a term infant
breech presentation
may be normal
What is the disadvantage to CTG monitoring during labour?
non-specific and increase medical intervention
Describe how to interpret a CTG.
Hint - Dr BrVADO
Define risks e.g. pre-eclampsia, diabetes Baseline foetal heart rate Variation in foetal HR Accelerations (>15bpm above baseline) Decelerations (>15bpm below baseline) Overall impression
What CTG changes are non-reassuring/abnormal?
Foetal bradycardia (HR<100) Foetal tachycardia (HR>160) Sinusoidal HR pattern <5 accelerations in 90 mins Late decelerations Reduced variability
What should be done if a CTG is non-reassuring?
inform senior move to left lateral position encourage fluids (IV or oral) Stop oxytocin Consider tocolysis
What should be done if you suspect an abnormal or pathological CTG?
inform senior
start conservative measures
offer foetal blood sampling
exclude factors that indicate need for immediate delivery (cord prolapse, uterine rupture, hyperstimulation, abruption)
Treat dehydration, hyperstimulation, hypotension and change position
What should be done if you suspect an abnormal or pathological CTG that requires urgent intervention?
Inform senior
start conservative measures
makes preparations for urgent birth (category 1 c-section)
When is foetal blood sampling indicated and how is it performed?
when their are abnormalities in foetal HR during labour and foetal acidosis is suspected
an amnioscope is used to obtain blood from the foetal scalp, cervix must be >3cm dilated
What is normal foetal pH?
7.25-7.35
What is the management plan if foetal blood pH is <7.2 and high lactate?
deliver - forceps or c-section
What are the 4Hs and 4Ts that can cause collapse that also need to be considered in pregnancy?
Hypovolaemia
Hypoxia
Hypo/hyperkalaemia
Hypothermia
Thromboembolism
Toxicity
Tension pneumothorax
Tamponade (cardiac)
What are the causes of maternal collapse isolated to pregnancy?
pre-eclampsia/ eclampsia
intracranial haemorrhage
What are the possible causes of maternal hypovolaemia in pregnancy?
bleeding
relative hypovolaemia of dense spinal block
septic or neurogenic shock
What are the possible causes of maternal hypoxia in pregnancy?
peripartum cardiomyopathy
myocardial infarction
aortic dissection
large vessel aneurysms
What are the possible causes for thromboembolism in pregnancy?
amniotic fluid embolism
pulmonary embolus
air embolus
myocardial infarction
How does an amniotic fluid embolism present?
acute respiratory distress and cardiovascular collapse in a patient during labour or in one who has recently delivered acute hypotension respiratory distress acute hypoxia seizures and cardiac arrest may occur
What are the complications of amniotic fluid embolism if the woman survives?
left ventricular dysfunction or failure
disseminated intravascular coagulation resulting in massive PPH
