1. Induction of Labour for Undergraduates
Max Brinsmead MB BS PhD
June 2017

2. Definition
Triggering uterine activity that will…
Ripen the cervix
Dilate the cervix
Deliver the baby
Note that Augmentation of Labour refers to stimulation of uterine activity that has spontaneously commenced

3. When to induce labour:
When the risks of continuing the pregnancy outweigh the risks of induction
Maternal reasons
Fetal reasons

4. Indications for Induction of Labour
Prolonged pregnancy
Ruptured membranes (at term)
Maternal pre eclampsia
For maternal diabetes
Fetus at Risk (IUGR or hypoxia)
Fetal death (or lethal malformation)
Chorioamnionitis
Maternal request incl. SOBP
Resources are optimal

5. How frequent is Induction of Labour?
If elective Caesarean section i.e. surgical delivery before the onset of labour, is included…
Then the incidence of IOL in contemporary obstetric practice exceeds 50% of all pregnancies

6. Agents for Induction of Labour
Mechanical
Sweep the membranes
Amniotomy – forewaters or hindwaters
Foley catheter
Uterine massage
Caesarean section
Pharmacological
Oxytocin
Prostaglandins

7. Sweeping the Membranes

8. Membrane Sweeping
Should be offered prior to formal induction of labour
Is not associated with any increased risk of fetal or maternal infection
Is painful (patients should be warned)
Will reduce the need for formal IOL for prolonged pregnancy if performed routinely at >40w

9. Amniotomy Tools - Amnihook

10. Amniotomy Tools - Amnicot

11. Amniotomy

12. Hindwater amniotomy tool The Drew-Smythe catheter

13. Foley catheter in the cervix

14. Mechanism of action of the mechanical methods that induce labour
All act by the local generation of…
PROSTAGLANDINS (PGs)
These 20-carbon, 5-ring eicosanoid fatty acids are autocrine and paracrine in action
Found in many tissues and synthesised by most nucleated cells
Fetal membranes and maternal uterine decidua are a rich source of several PGs that have TWO uterine effects

15. The Uterine Effects of Prostaglandins
Ripening the cervix by:
Altering its connective tissue composition
Increasing its fluid content
This takes some time, >24 hours
Effective at any gestation
PGs also stimulate uterine smooth muscle to contract
This is referred to as its “oxytocic effect”
Can occur immediately
The half life of some PGs is milliseconds

16. Oxytocin A classic hormone released from the posterior pituitary
Neuro endocrine in its control
It is a nonapeptide
Closely related to Anti diuretic hormone (ADH) or Vasopressin
Has roles in sexual bonding, orgasm, milk letdown and labour
Syntocinon is the synthetic form of oxytocin
Has a half life of 2 hours in the circulation

17. Syntocinon in Use Administered only by IV infusion
Typically begins with a low dose (1 mU/min)
Increase by doubling every 30 – 60 min according to the uterine response to a maximum of 32 mU/min
Not very effective before term because of absent receptors in myometrium
Used to both induce and augment labour
Not very effective when membranes are intact
Used in high doses postpartum to contract the uterus and protect from PPH

18. Prostaglandins in Use
Best administered as a vagina gel or tape/pessary
But can be injected directly into the myometrium of the uterus in the treatment of PPH
Or given per rectum
“Prostin” is PGE2 and comes in 1 mg & 2 mg doses
“Cervidil” is PGE2 available as a tape in Australia
“Cervagem” is gemeprost, a 1 mg pessary that is used to ripen the cervix or terminate pregnancy, causes fetal death in utero
“Cytotec” is misoprostol that is used for TOP. Its oral use for induction of labour is controversial

19. Adverse Outcomes from Attempted Induction of Labour
Failed induction
May not have waited long enough or tried for long enough
“Fetal distress”
By causing uterine hypercontractility
Cord compression FHR decelerations
True fetal hypoxia is more common if there is placental compromise
The need to monitor reduces maternal options
Chorioamnionitis
A consequence of amniotomy and multiple vaginal exams
Cord prolapse during amniotomy
Will not occur if the head is “engaging” and filling the true pelvis

20. Less common outcomes from Attempted Induction of Labour
Increased risk of postpartum haemorrhage
Averted by high dose Syntocinon infusion after delivery
Uterine rupture
Mostly a problem after previous Caesarean
Amniotic fluid embolism
Syntocinon with intact membranes
Water intoxication (ADH effect of high dose Syntocinon)
Abruption of the placenta
Amniotomy with polyhydramnios
Fetal bleeding from vasa previa

21. Vasa Previa

22. How to induce labour:
For prolonged pregnancy first sweep the membranes
For ruptured membranes…
Oxytocin by IV infusion
Although wait-and-see and vaginal PG’s are acceptable
For all other patients (except those with a uterine scar)…
Vaginal prostaglandins
Regardless of the state of the cervix or the parity of the patient
Amniotomy followed by oxytocin infusion 3 – 12 hours later is likely to be the most cost effective when the cervix is ripe

23. Induction of labour after Previous Caesarean
For spontaneous labour the risk of scar rupture is 1:200
With oxytocin infusion the risk is 1:100
With prostaglandins the risk is 1:40
More difficult to induce?
Direct effect of PG’s on connective tissue?
Foley catheter is an acceptable alternative

24. Fetal surveillance during Induction of Labour
Fetal wellbeing should be established prior to induction of labour.
After vaginal prostaglandins check fetal wellbeing when contractions are detected or reported.
Use CTG. If it is normal, and labour has been triggered, then intermittent monitoring can be used.
But continuous CTG is required whenever oxytocin is infused

25. Hypercontractility with Oxytocin
If the CTG is suspicious or abnormal then stop the infusion
If fetal compromise is suspected or confirmed then deliver ASAP taking account the severity of CTG changes and relevant maternal factors – ideally within 30 min
Or restart the oxytocin after not less than 60 min, at half dose and only if the CTG is normal

26. Using Prostaglandins
The risk of hypercontractility with or without FHR changes is 1-5%
Women should lie down for 30 min after PGs are inserted
Oxytocin should not be started within 6 hours of PG insertion

27. Hypercontractility with PGs
Remove any gel
Irrigation is not beneficial
Short term maternal O2 may help
Uterine tocolysis with a betamimetic can be useful

28. The 1st recommendation of the RCOG concerning Induction of Labour
Women must be able to make informed choices regarding their care with evidence-based information.
These choices should be recognised as an integral part of the decision-making process.
Give them a handout to reinforce this

30. Any Questions or Comments
Please leave a note on the Welcome Page to this website