Labour , Preterm & CS Flashcards
What are the 3 stages of labour?
- First Stage - onset defined by progressive contractions and cervical changes
a. Latent first stage - effacement (thinning) of cervix, dilatation to 3cm
b. Active first stage - dilatation from 3 - 10cm (i.e. fully dilated) - Second stage - from full dilation to delivery of the baby
a. Passive second stage - head descends down pelvis
b. Active second stage - mother bears down - Third stage - from delivery of baby to delivery of placenta and membranes
- Should occur within 30 minutes of delivery of the baby
- Can be physiological (i.e. no intervention) or actively managed (oxytocin
injection after delivery of anterior shoulder).
What is myometrial activation?
uterine contractions become synchronised and coordinated at term
What are the 3 stages of myometrial activation?
- Endocrine cascade triggered by foetus leads to increased maternal oestrogen and decreased
progesterone. Other contributing factors include uterine stretch, cortisol and the Ferguson reflex. - This leads to expression of CAPs (contraction-associated proteins) and increased production of oxytocin
and prostaglandins. - CAPs increase expression of oxytocin receptors, prostaglandin receptors, gap junction proteins and ion
channels to facilitate contractions.
- This is heavily simplified - the idea is that both agonists and receptors are increased to initiate labour.
What are the 7 levels of the second stage of labour?
- Descent - the baby’s head (providing it is in cephalic presentation) descends deeper into
the pelvis until it is no longer palpable on abdominal examination. - Flexion - the baby’s head flexes (chin to chest) to give the narrowest
(suboccipitobregmatic) diameter. - Internal rotation - baby’s occiput rotates anteriorly from the lateral position to give the
normal occipito-anterior position.
The Peer Teaching Society is not liable for any false or misleading information. 21 - Extension - baby’s occiput contacts the maternal pubic rami - it then extends and
crowns - Restitution - baby’s occiput re-aligns with its shoulders, which lie in between the
anterior-posterior and lateral positions - External rotation - baby’s shoulders rotate into anterior-posterior position (i.e.
perpendicular to mother’s). At this point, the baby’s head is delivered - it is aligned with
its shoulders, so the face looks laterally at the mother’s thigh. - Delivery of shoulders - the anterior shoulder is delivered first from beneath the pubic
ramus; the head is then gently lifted anteriorly to deliver the posterior shoulder. The rest
of the baby’s body rapidly follows.
When monitoring labour, what do we do for the initial assessment?
Initial Assessment:
- Take a history, assess for risk factors, assess for pain.
- Pulse, blood pressure, respiratory rate, urinalysis
- Abdominal palpation to determine lie, presentation, engagement, contraction strength.
- Vaginal examination to determine station, position, cervical effacement and dilatation,
presence or absence of membranes, caput or cranial moulding.
Where is progression of labour, foetal and maternal well being recorded on?
Partogram
What are the measurements of a partogram?
- Progress: cervical dilatation, descent, contractions (frequency and duration)
- Foetal wellbeing: heart rate*, amniotic fluid (liquor)
- Maternal wellbeing: pulse, blood pressure, temperature, urinalysis
How can HR be monitored in babies?
Heart rate can be monitored by intermittent auscultation with a Doppler probe (in low risk
deliveries) or continuously with a cardiotocograph (CTG, in higher risk deliveries).
How are CTG readouts interpreted?
- Normal: no non-reassuring features
- Suspicious: one non-reassuring feature
- Pathological: two non-reassuring features or one abnormal features
What are reassuring features of the CTG?
- Baseline heart rate: 110-160
- Decelerations (drops of 15 bpm for 15s): absent
- Accelerations (increases of 15 bpm for 15s): present
- Baseline variability: 5-25 bpm
What are some non-reassuring features features of the CTG?
- Baseline heart rate: 100-109 / +20
from start of
labour - Decelerations (drops of 15 bpm for 15s): Repetitive variable for
<30 mins / variable for
<30 mins / repetitive late
for 30 mins - Accelerations (increases of 15 bpm for 15s): absent
- Baseline variability: <5 for 30-50 mins />25 for <10 mins
What are some abnormal features of a CTG?
- Baseline heart rate: <100 / >160
- Decelerations (drops of 15 bpm for 15s): Repetitive variable with
concerning
characteristics >30 mins /
repetitive late >30 mins /
3 min bradycardia - Accelerations (increases of 15 bpm for 15s): absent
- Baseline variability: <5 for 50 mins / >25
for >10 mins /
sinusoidal pattern
How are some ways to cause analgesia in labour?
- Non-pharmacological: breathing and relaxation techniques / use of birthing pool
- Non-regional: Entonox (‘gas and air’ - 50:50 mix of nitrous oxide and oxygen),
intramuscular opioids e.g. diamorphine or morphine - Regional: Epidural - local anaesthetic e.g. bupivacaine combined with fentanyl bolused
into L3-4 epidural space, where it acts upon nerve roots to provide analgesia. N.B. a
‘passive hour’ without active pushing upon full dilatation is required.
What are the indications which would lead to the induction of labour?
- Prolonged pregnancy >41 weeks
- Preterm prelabour rupture of membranes (usually offered at 37+0)
- Term prelabour rupture of membranes (offer 24hrs expectant management as well)
- Maternal request
- Maternal health issues e.g. pre-eclampsia, obstetric cholestasis
- Intrauterine foetal death (IUFD) - previously
What are the methods to cause induction of labour?
- Membrane sweep: finger passed through cervix to separate part of the chorionic
membrane from the decidua; offered from 39+0. - Bishop Score <6: prostaglandin E2 pessary (dinoprostone) or osmotic dilator
- Bishop Score >6: amniotomy (artificial rupture of membranes) +/- oxytocin infusion.
What are the 3 stages of delay in labour
● First Stage: cervical dilatation of less than 2cm in 4 hours.
● Second Stage:
○ Nulliparous: >2 hour duration of second stage of labour.
○ Multiparous: >1 hour duration of second stage of labour.
● Third Stage:
○ Actively managed (oxytocin injection): >30 minutes without delivery of placenta.
○ Physiological: >60 minutes without delivery of placenta.
What are the 3 Ps of delayed labour?
Power:
- Uterine contractions - deviation from normal (i.e. 3-5 contractions of 30 seconds
duration per 10 minutes).
- Passenger:
- Size of foetus (head diameter, shoulder diameter etc.)
- Foetal presentation (cephalic: vertex, brow, face vs breech)
- Foetal position (occipito-anterior (normal), occipito-posterior, occipito-transverse)
- Passage:
- Cephalopelvic disproportion
What are the investigations for delayed labour?
● Diagnosed by regular foetal monitoring in labour.
● Aberrant foetal position can be diagnosed on vaginal examination
What is the management for 3 different stages of delayed labour?
● First Stage:
○ Membranes intact - consider amniotomy.
○ Consider oxytocin infusion - requires continuous foetal monitoring (CTG).
● Second Stage:
○ Consider oxytocin infusion.
○ Offer expedited delivery i.e. instrumental delivery or caesarean section if
vaginal delivery is improbable.
● Third Stage:
○ Controlled cord traction, IM oxytocin / ergometrine.
Officially you are preterm up to…?
36 weeks 6 days 23 hours 59 minutes and 59 seconds
Delivery prior to 37 weeks gestation:
- <28 weeks: Extremely Preterm
- 28-32 weeks: Very Preterm
- 32-37 weeks: Moderate to Late Preterm
What is the most accurate method of dating?
The most accurate method of dating is based on the measurement of a crown-rump length of a fetus on a first trimester scan.
What are the admissions for neonatal care
Approximately 10% of newborn infants require admission for neonatal care
So with 7000 babies per year at Jessops
800 come to NNU
Preterm - about 360
Term - about 240
Epidemiology of preterm birth
Approximately 10% of births globally are preterm
7.8% of births in the UK are preterm
Significant geographical variation with rates varying from 6.8% (east Asia/Oceania) to 13.2% (southern Asia) in 2020
Discrepancy in quality of data
What percentage of all births are preterm births and at what gestation age (weeks) do they happen?
0.5% = 20 -27
1% = 28-31
4.5% = 32-36
What is the background for instrumental delivery?
- AKA assisted vaginal birth (by forceps or vacuum).
- 10-15% of deliveries in the UK; ⅓ of first deliveries for nulliparous women
What are the types of instrumental delivery?
● Forceps delivery:
○ Interlocking blades fit around the baby’s head and guide it down the birth canal,
typically alongside medio-lateral episiotomy.
● Vacuum delivery:
○ Suction cup adheres to the baby’s head to assist with delivery.
What are the assisted vaginal birth classifications?
- Outlet - visible foetal scalp, skull has reached perineum, rotation less than 45 degrees.
- Low Cavity - station +2cm but not reaching perineum.
- Mid Cavity - less than 1/5th palpable abdominally, station +1 to 0cm
What are the rotational instruments used for an instrumental delivery?
- Kjelland’s forceps
- Posterior cup e.g. Kiwi
What are the non-rotational instruments for instrumental delivery?
- Neville Barnes forceps (low-cavity)
- Simpson’s forceps
- Wrigley forceps (outlet, also used in caesarean sections)
- Anterior cup
What are the indications for instrumental delivery?
- Suspected foetal compromise
- Delayed second stage
- Maternal exhaustion / distress
- Medical contraindication to Valsalva
What are the risks and complications of forceps delivery?
- Vaginal trauma
- Postpartum haemorrhage
- Obstetric anal sphincter injury (3rd degree tear)
- Facial / scalp laceration
What are the risks of vacuum delivery?
- Vaginal trauma
- Postpartum haemorrhage
- OASI
- Facial / scalp laceration
- Retinal haemorrhage
- Cephalohematoma
- Subgaleal haemorrhage
What are the types of obstetric injuries?
● 1st Degree Tear: skin only
● 2nd Degree Tear: perineal muscle
● 3rd Degree Tear: anal sphincter complex
○ Type A = less than 50% external AS
○ Type B = more than 50% external AS
○ Type C = internal and external AS injury
● 4th Degree: anorectal epithelium
What are the classifications of urgency for a Caesarean section (CS)?
● Category 1 - within 30 minutes of decision - immediate threat to life of woman or foetus
e.g. pathological CTG, placental abruption.
● Category 2 - within 75 minutes of decision - maternal / foetal compromise, not
immediately life-threatening but birth must be expedited.
● Category 3 - no compromise, early birth indicated.
● Category 4 - elective.
What are the indications for a CS?
- Breech presentation (resistant to external cephalic version).
- Placenta praevia
- Placenta accreta spectrum
- Maternal choice
- Emergency: foetal bradycardia, abruption, uterine rupture, cord prolapse, foetal pH <
7.20, failure of instrumental delivery.
What is the definition of a preterm labour?
● Onset of labour before 37 weeks gestation.
What is the pathophysiology of preterm labour?
● Similar mechanism to normal labour - probably due to:
○ Premature uterine stimulation
○ Premature withdrawal of pro-quiescent factors.
● Generally dictated by an inflammatory process causing prostaglandin release, such as:
1. Intrauterine infection
2. Placental ischaemia / decidual haemorrhage
3. Uterine stretch
4. Foetal / maternal stress
What does labour involve?
Labour involves a common downstream pathway of cervical remodelling, uterine activity and decidua/membrane activation.
What are the four phases of cervical remodelling?
Softening
Ripening
Dilation
Repair
What are the 2 primary mechanical functions of the cervix?
provide a strong outlet to the uterus until an appropriate gestation and then to become compliant and dilate to allow passage of the fetus.
Physiology of the cervix
Softening is a gradual process beginning in the first trimester that does not result in the loss of cervical integrity.
Ripening occurs as gestation advances, resulting in rapid increase in compliance and loss of strength.
Dilatation occurs when uterine contractions occur in the presence of a ripened cervix.
The triggers for these changes are variable, but the results are immune cell infiltration, matrix metalloproteinase activation resulting in ECM degradation, an increase in hyaluronic acid, increased hydration of the ECM, and weakening of the collagen network.
Result is of a softer, shorter and weaker structure which is able to stretch and dilate in response to uterine contractions
How can infection cause preterm labour?
25-40% of preterm birth may be due to infection
Most commonly intrauterine bacterial infections
Organisms include Ureaplasma urealyticum, streptococcus agalactiae, E. Coli, fusobacterium and Gardnerella
Pathways of intra-amniotic infection:
Ascending from vagina and cervix
Transplacental infection (haematogenous)
Retrograde seeding from peritoneal cavity through fallopian tube
Iatrogenic during invasive procedures e.g. amniocentesis
Infection triggers pro-inflammatory cytokines which can cause uterine contractility, membrane rupture and cervical ripening
How can ischaemia cause preterm labour?
Most common placental finding in those cases without infection/inflammation
Maternal or fetal vascular lesions such as failure of transformation of the myometrial segment of spiral arteries, thrombosis of spiral arteries, reduced number of fetal arterioles in villi.
Would account for both intrauterine growth restriction/pre-eclampsia and preterm birth.
How can uterine overdistension cause preterm labour?
Risk factors:
Structural uterine anomalies
Polyhydramnios
Multiple pregnancy
Stretching can induce myometrial contractility, prostaglandin release, expression of gap junction proteins and increased oxytocin receptors.
