Induction of Labour Flashcards
What is meant by induction of labour?
- an intervention to initiate the onset of labour
- this is performed when the benefits of ending the pregnancy outweigh those of continuing it
AND
- where vaginal birth is considered appropriate
the health of the mother and the foetus must be taken into account
When is IOL typically offered?
- when patients surpass their due date
- typically between 41-42 weeks gestation
- it can also be performed at other times in situations when it is beneficial to start labour early
In what situations may it be beneficial to start labour early?
- premature rupture of the membranes (PROM)
- foetal growth restriction
- pre-eclampsia
- obstetric cholestasis
- existing diabetes
- intrauterine foetal death
What must be considered when inducing labour prior to 39 weeks?
- there is an increased prevalence of special educational needs with earlier IOL
- this is significant when IOL occurs prior to 37 weeks gestation
IOL at 39 weeks is not associated with increased risks such as C-section, foetal morbidity or instrumental delivery
What should always be explained to a woman considering IOL?
- the reason the induction is being offered
- the risks and benefits in their situation
- that IOL may not be successful and other options
- an alternative if the woman denies IOL
Why is IOL performed in prolonged pregnancy?
(between 41-42 weeks)
- when pregnancy extends past the due date, there is an increase in perinatal mortality
- this is due to decreased placental function
- all healthy women should be offered IOL when pregnancy extends beyond 41 weeks
What are the absolute contraindications to IOL?
- acute foetal compromise
- unstable lie (transverse lie = indication for CS)
- placenta praevia
- acute foetal compromise requires immediate delivery and IOL takes time
What are the relative contraindications to IOL?
- previous C-section
- breech presentation
- prematurity
- high parity
many of the contraindications are due to insuitability of vaginal delivery
Why is previous C-section a relative contraindication to IOL?
- there is a 1 in 200 risk of uterine scar rupture in VBAC
- the risk of uterine rupture is increased by 3-4 x when IOL is used
- continuous monitoring is needed to look for signs of uterine rupture
VBAC = vaginal birth after C-section
When is IOL offered for intrauterine foetal death?
- IOL is offered immediately
OR
- expectant management is appropriate if no signs of infection / bleeding + intact membranes
- immediate IOL is required if there is signs of infection, bleeding or ruptured membranes
What is the regime for IOL following intrauterine foetal death?
oral mifeprestone
followed by misoprostol (oral / vaginal)
- misoprostal 100 micrograms 6 hourly if < 26+6 weeks
- misoprostal 25-50 micrograms 4 hourly if 27 weeks or more
- NOT suitable for use when baby is alive
What scoring system is used to determine whether to induce labour?
Bishop score
score from 0 to 13
What is involved in calculating the Bishop score?
- it involves a vaginal examination to assess 5 areas
- fetal station
- cervical consistency
- cervical position
- cervical dilatation
- cervical effacement
What Bishop score indicates IOL is suitable?
- a score of 8 or more predicts successful IOL
- a score below 8 indicates cervical ripening may be required to prepare the cervix
this assesses whether it would be possible for artificial rupturing of the membranes (ARM)
What procedure is often performed prior to IOL?
membrane sweep
- this is provided as an assistance before full induction of labour is offered
What is involved in membrane sweep?
- a finger is inserted into the cervix and rotated against the wall of the uterus
- this separates the chorionic membrane from the decidua and begins the process of labour
- if successful, it should produce the onset of labour within 48 hours
When is membrane sweep offered?
- it is used from 40 weeks gestation to attempt to initiate labour in women over their EDD
- it cannot be offered prior to 37/38 weeks as the cervix needs to be ripe in order to allow insertion of the finger
What is the main method of IOL?
artificial rupture of membranes (ARM)
- an amniohook is inserted through the partially opened cervix to create a hole in the membranes
- this increases pressure of the fetal head on the cervix + results in hormonal reactions
Following successful ARM, what is done for women who have not been pregnant before?
augmentation:
- exogenous oxytocin is given via a slow IV drip
- this is syntocinon
- syntocinon is started at 2ml/hour and slowly titrated to achieve regular contractions
the aim is to achieve 3-4 contractions every 10 mins
What is the main complication associated with augmentation?
hyperstimulation
this is avoided by giving a slow IV drip
Following successful ARM, what is offered to women who have previously been pregnant?
- there is a delay of 4-6 hours to allow them to mobilise
- they are more likely to have uterine contractions without exogenous oxytocin
- syntocinon is given if contractions do not occur
What is the preferred method of IOL?
cervical ripening:
- this involves use of vaginal prostaglandin E2 (dinoprostone)
- this is inserted as a gel, tablet (Prostin) or pessary (Propess) into the vagina
- the pessary is similar to a tampon and slowly releases prostaglandins over 24 hours
Can cervical ripening be repeated?
- after the pessary has been in place for 24 hours, the woman is reassessed
- their suitability for ARM is reconsidered
- if still unsuitable, the another pessary is inserted for 24 hours
- this can be repeated up to 3 times
What is a cervical ripening balloon (CRB)?
- a silicone balloon is inserted into the vagina
- it is gently inflated to dilater the cervix
- this is used when vaginal prostaglandins are not preferred
