2.03 - Labour and Delivery Flashcards
Between which gestational weeks in labour and delivery normal?
G37-G42
Define the
a) first stage
b) second stage
c) third stage
of labour.
a) onset of labour (true contractions) until 10cm cervical dilatation.
b) from 10cm cervical dilatation until delivery of the baby.
c) from delivery of the baby until delivery of the placenta.
What are the phases of the first stage of labour?
Give the cervical measurement range, expected progression and characteristic of contractions for each phase.
Latent phase from 0-3cm dilation of the cervix. This progresses at around 0.5cm per hour. There are irregular contractions.
Active phase from 3-7cm dilation of the cervix. This progresses at around 1cm per hour. There are regular contractions.
Transition phase from 7-10cm dilation of the cervix. This progresses at around 1cm per hour. There are strong and regular contractions.
What are Braxton-Hicks contractions?
Occasional and irregular contractions of the uterus felt during T2-T3.
These are not true contractions and DO NOT indicate the onset of labour.
Staying hydrated and relaxing can help reduced Braxton-Hicks contractions.
What are the signs of labour?
- show (mucus plug from the cervix)
- rupture of membranes
- regular, painful contractions
- dilating cervix on examination
According to NICE (2017), the latent first stage of labour is when there are both:
- painful contractions
- effacement and dilation of the cervix
According to NICE (2017, the established first stage of labour is when there are both:
- regular, painful contractions
- dilation of the cervix ≥4cm
Define the following terms:
a) rupture of membranes (ROM)
b) spontaneous rupture of membranes (SROM)
c) premature rupture of membranes (PROM)
d) preterm prelabour rupture of membrane (P-PROM)
e) prolonged rupture of the membranes (PROM)
a) amniotic sac has ruptured
b) amniotic sac has ruptured spontaneously
c) amniotic sac has ruptured before the onset of labour
d) amniotic sac has ruptured before the onset of labour and before 37 weeks gestation (preterm)
e) the amniotic sac ruptures more than 18 hours before delivery
Define prematurity.
Birth before 37 weeks.
When is a premature baby considered non-viable?
Below 23 weeks gestation.
Generally, from 23 to 24 weeks, resuscitation is not considered in babies that do not show signs of life.
Babies born at 23 weeks have ~10% chance of survival.
World Health Organisation classes prematurity as:
a) <28 weeks
b) 28-32 weeks
c) 32-37 weeks
a) extreme preterm
b) very preterm
c) moderate to late preterm
What are the options for prophylaxis of preterm labour?
- vaginal progesterone
- cervical cerclage
Outline the role of vaginal progesterone in the prophylaxis of preterm labour.
Progesterone decreases the activity of the myometrium and prevents cervix remodelling in preparation for delivery.
Offered to women with a cervical length <25mm on vaginal ultrasound between 16 to 24 weeks gestation.
Outline the role of cervical cerclage in the prophylaxis of preterm labour.
Involves putting a stitch in the cervix to add support and keep it closed, under spinal or general anaesthetic. The stitch is removed when the woman goes into labour or reaches term.
Offered to women with a cervical length <25mm on vaginal ultrasound between 16 and 24 weeks gestation, who have had previous premature birth or cervical trauma.
How is preterm prelabour rupture of the membranes diagnosed?
Diagnosed by speculum examination revealing pooling of amniotic fluid in the vagina. No tests are required.
If there is doubt around the diagnosis of P-PROM, what tests can be performed?
IGFBP-1 is a protein present in high concentrations in amniotic fluid, which can be tested on vaginal fluid if there is doubt about rupture of membranes.
PAMG-1 is a similar alternative to IGFBP-1.
How is P-PROM managed?
Prophylactic erythromycin 250mg QDS for ten days, or until labour is established if within 10 days, to prevent the development of chorioamnionitis.
Induction of labour offered from 34 weeks gestation.
What is preterm labour with intact membranes?
Regular, painful contractions and cervical dilatation, without rupture of the amniotic sac and before 37 weeks gestation.
According to NICE (2017), how is preterm labour with intact membranes diagnosed
a) less than 30 weeks gestation?
b) more than 30 weeks gestation?
a) speculum examination to assess for cervical dilatation.
b) transvaginal ultrasound showing cervical length <15mm.
Outline the several options for improving the outcomes in preterm labour.
- fetal monitoring (CTG or intermittent auscultation)
- tocolysis
- maternal corticosteroids
- IV magnesium sulphate
- delayed cord clamping
Describe the role of tocolysis in preterm labour.
The use of medications (e.g. nifedipine, atosiban) to stop uterine contractions and delay delivery:
- allows time for further fetal development
- antenatal steroid administration
- transfer to specialist unit (NICU)
Used between 24 and 33+6 weeks gestation, allowing delay up to 48 hours.
Describe the role of antenatal steroids in premature labour.
Two doses of IM betamethasone, 24 hours apart, administered to mother.
Helps develop the fetal lungs and reduce respiratory distress syndrome after delivery.
Used in women with suspected premature labour of babies less than 36 weeks gestation.
Describe the role of magnesium sulphate in premature labour.
IV magnesium sulphate protects the fetal brain during premature labour, reducing the risk of cerebral palsy.
Given within 24 hours of delivery of preterm babies less than 34 weeks gestation:
- bolus
- infusion for 24 hours or until birth
What monitoring is required if administering IV magnesium sulphate?
Monitoring for magnesium toxicity at least four hourly:
- bradypnoea
- hypotension
- areflexia
What is induction of labour (IOL)?
Use of medications to stimulate the onset of labour.
Indications for IOL.
- G41-G42
- prelabour rupture of membranes
- fetal growth restriction
- pre-eclampsia
- obstetric cholestasis
- existing diabetes
- intrauterine fetal death
Describe the scoring system used to decide whether to induce labour?
Bishop score assesses:
- fetal station (max 3)
- cervical position (max 2)
- cervical dilatation (max 3)
- cervical effacement (max 3)
- cervical consistent (max 2)
A score ≥8 predicts a successful induction of labour.
A score ≤7 suggests cervical ripening required to prepare the cervix.
What are the options for IOL?
- membrane sweep
- vaginal prostaglandin E2
- cervical ripening balloon
- artificial rupture of membranes
Describe the role of membrane sweep in IOL.
Involves inserting a finger into the cervix to stimulate it and begin the process of labour within 48 hours.
It is used from 40 weeks gestation to attempt to initiate labour in women over the EDD.
Describe the role of vaginal prostaglandin E2 in IOL.
Insertion of a pessary into the vagina that slowly released local prostaglandins over 24 hours. This stimulates the cervix and uterus to cause the onset of labour.
Usually done in the hospital setting so women can be monitored, before being allowed home to await the full onset of labour.
Describe the role of cervical balloon ripening (CBR) in IOL.
Insertion and inflation of a balloon to dilate the cervix.
Used in women with a previous caesarean section, where vaginal prostaglandins have failed or in multiparous women.
Describe the role of artificial rupture of membranes in IOL.
Oxytocin infusion to induce labour if vaginal prostaglandins have been unsuccessful.
What medications can be given to induce labour in the case of intrauterine fetal death?
Oral mifepristone plus misoprostol.
What monitoring is required in IOL.
Cardiotocography (CTG) to assess fetal heart rate and uterine contractions, before and during induction of labour.
Bishop score before and during induction of labour to monitor the progress.
When there is slow progress following IOL, what are the options?
Most women will give birth within 24 hours of IOL. If they have not:
- further vaginal prostaglandins
- artificial rupture of membranes
- CRB
- elective caesarean section
What is the main complication of induction of labour with vaginal prostaglandins?
Uterine hyperstimulation.
Contraction of the uterus is prolonged and frequent, causing fetal distress and compromise.
What are the criteria for uterine hyperstimulation.
≥5 contractions in 10 minutes
or
painful contractions lasting ≥90s
PLUS ABNORMAL CTG
What are the complications of uterine hyperstimulation?
- fetal compromise (hypoxia and acidosis)
- emergency caesarean section
- uterine rupture
Management of uterine hyperstimulation.
- removal of vaginal prostaglandins
- stopping oxytocin infusion
- tocolysis with terbutaline*
*Hyperstimulation should resolve within 15-20 minutes due to short half life of vaginal prostaglandins. Consider tocolysis if no spontaneous resolve within this timeframe.
What measurements can be taken from cardiotocography (CTG)?
- fetal heart rate
- contractions of the uterus
Two tranducers are placed on the abdomen to get the CTG readout:
- one above the fetal heart to monitor the fetal heartbeat
- one near the fundus of the uterus to monitor uterine contractions
Indications for continuous CTG monitoring.
- maternal sepsis
- maternal tachycardia (>120)
- pre-eclampsia
- antepartum haemorrhage
- delay in labour
- use of oxytocin
- significant meconium
- disproportionate maternal pain
Give a mnemonic used to assess CTGs.
DR C BRaVADO
DR - Define Risk based upon individual woman and pregnancy before assessing CTG.
C - Contractions
BRa - Baseline Rate
V - Variability
A - Accelerations
D - Decelerations
O - Overall impression
Give some reasons a pregnancy may be considered high risk.
Maternal medical illness:
- gestational diabetes
- hypertension
- asthma
Obstetric complications:
- multiple gestation
- post-date gestation
- previous caesarean section
- intrauterine growth restriction
- PROM
- oxytocin induction
- pre-eclampsia
Other risk factors:
- absence of prenatal care
- smoking
- drug abuse
Interpretation of contractions on CTG.
Assess the number of contractions present in a 10 minute period.
How long do the contractions last?
How strong are the contractions (assessed using palpation)?
Define the following terms and their respective CTG findings:
a) tachysystole
b) hypertonus
c) uterine hyperstimulation
a) ≥5 contractions in 10 minutes, with normal CTG
b) painful contraction lasting ≥90s, with normal CTG
c) tachysystole or hypertonus, with abnormal CTG
Interpretation of baseline rate of fetal heart on CTG.
Average heart rate of a fetus within a 10-minute window.
Normal fetal heart rate is between 110-160bpm.
Define fetal tachycardia and suggest some causes.
Baseline heart rate >160bpm:
- fetal hypoxia
- chorioamnionitis
- hyperthyroidism
- anaemia
Define fetal bradycardia.
Baseline heart rate <110bpm
When is it common to have a baseline heart rate between 100-120bpm?
- postdate gestation
- occiput posterior presentation
- occiput transverse presentation
Define severe prolonged fetal bradycardia and suggest some causes.
Baseline heart rate less than 80bpm for >3 minutes, indicating severe hypoxia:
- prolonged cord compression
- cord prolapse
- epidural and spinal anaesthesia
- maternal seizures
- rapid fetal descent
Interpretation of variability on CTG.
The variation in fetal heart rate from one beat to the next.
Normal variability is between 5-25bpm, indicating an intact neurological system in the fetus.
Define
a) reassuring variability
b) non-reassuring variability
c) abnormal variability
on CTG.
a) 5-25bpm
b) less than 5bpm for >30 minutes, or more than 25bpm for >15 minutes
c) less than 5bpm for >50 minutes, or more than 25bpm for >25 minutes.
Causes of reduced variability on CTG.
Fetal sleeping (should last no longer than 40 minutes).
Fetal acidosis due to hypoxia.
Fetal tachycardia.
Drugs (e.g. opiates, benzodiazepines, magnesium sulphate).
Prematurity <28 weeks.
Congenital heart abnormalities.
Interpretation of accelerations on CTG.
Accelerations are an abrupt increase in the baseline fetal heart rate of greater than 15bpm >15s.
Accelerations occuring alongside uterine contractions is a sign of a healthy fetus.
NB the absence of accelerations in an otherwise normal CTG is of uncertain significance.
Define and give the physiology of decelerations on CTG.
Abrupt decrease in the baseline fetal heart rate of greater than 15bpm for >15s.
In response to hypoxic stress, the fetus reduces its heart rate to preserve myocardial oxygenation and perfusion.
Give the types of decelerations present on CTG.
- early deceleration
- variable deceleration
- late deceleration
- prolonged deceleration
What is early deceleration?
When uterine contraction begins, increased fetal intracranial pressure increases vagal tone, reducing heart rate.
When uterine contractions end, fetal ICP reduces and vagal tone follows.
This type of deceleration is PHYSIOLOGICAL.
What is a variable deceleration?
The rapid fall in baseline fetal heart rate with a variable recovery phase, sometimes with no relationship to uterine contractions.
They are variable in their duration and is PATHOLOGICAL.
Mechanism of variable decelerations.
Umbilical cord compression:
1) Umbilical vein is occluded, causing acceleration of the fetal heart rate in response.
2) Umbilical artery is occluded, causing a subsequent rapid deceleration.
3) When pressure on the cord is reduced, another acceleration occurs and the baseline heart rate returns.
What is late deceleration?
Beginning at the peak of the uterine contraction, due to insufficient blood flow to the uterus and placenta.
There is recovery after the contraction ends.
Causes of reduced uteroplacental blood flow include:
- maternal hypotension
- pre-eclampsia
- uterine hyperstimulation
What is prolonged deceleration?
Deceleration lasting more than 2 minutes.
Non-reassuring if lasting between 2-3 minutes.
Abnormal if lasting longer than 3 minutes.
What is sinusoidal CTG pattern?
Sinusoidal CTG pattern has the following characteristics:
- smooth, regular, wave-like pattern
- frequency of 2-5 cycles a minute
- stable baseline rate
- no beat to beat variability
What are the causes of sinusoidal CTG pattern?
Associated with high rates of fetal morbidity and mortality:
- severe fetal hypoxia
- severe fetal anaemia
- fetal haemorrhage
- maternal haemorrhage
How can overall CTG impression be described?
- reassuring
- suspicious: a single non-reassuring feature
- pathological: two non-reassuring features or a single abnormal feature
- need for urgent intervention: acute bradycardia or prolonged deceleration of more than 3 minutes
How can abnormal CTG be managed?
- escalate to senior midwife and obstetrician
- further assessment for possible causes (e.g. uterine hyperstimulation, maternal hypotension, cord prolapse)
- conservative interventions (e.g. repositioning of mother, giving IV fluids for hypotension)
- fetal scalp stimulation
- fetal scalp blood sampling to test for fetal acidosis
- delivery of baby (instrumental delivery or emergency caesarean section)
What are the rule of 3s for fetal bradycardia?
3 minutes - call for help
6 minutes - move to theatre
9 minutes - prepare for delivery
12 minutes - deliver the baby
What is the role of oxytocin during labour?
Stimulates ripening of the cervix and contractions of the uterus.
What is the role of syntocinon in labour and delivery?
Synthetic infusion of oxytocin used to:
- induce labour
- progress labour
- improve frequency and strength of uterine contractions
- prevent or treat postpartum haemorrhage
What is the role of atosiban in labour and delivery?
Oxytocin receptor antagonist used as an alternative to nifedipine.
Action in tocolysis in premature labour.
Outline the role of ergometrine in labour and delivery.
Stimulates smooth muscle contraction in the uterus and blood vessels.
Used in the third stage of labour to induce delivery of the placenta.
Used postpartum to prevent and treat postpartum haemorrhage.
What are the side effects of ergometrine?
- hypertension*
- diarrhoea
- vomiting
- angina
*avoid in eclampsia
What is the role of prostaglandins in labour and delivery?
Stimulate contraction of uterine muscles and ripen the cervix before delivery.
Dinoprostone (prostaglandin E2) is used for IOL:
- vaginal pessaries
- vaginal tablets
- vaginal gel
Why are NSAIDs avoided during pregnancy?
Prostaglandins act as vasodilators, and lower blood pressure.
NSAIDs inhibit the action of prostaglandins, so can increase blood pressure.