Induction of labour (IOL) is the stimulation of your womb to start labour. Your obstetrician will discuss with you the reasons why IOL is being offered. You may be examined at the time of deciding for induction to determine the best method of induction for you. At this time you will be offered a ‘membrane sweep’. This is when the membranes (the bag of water surrounding your baby) are manually separated from the cervix (neck of the womb). It can be a little more uncomfortable than a routine internal examination, but it releases natural hormones which may start your labour spontaneously or make IOL quicker and easier.
The benefits of IOL vary with the reason for induction. For those being offered IOL for being more than 10 days overdue, IOL offers: a) a reduction in the risk of stillbirth and b) no increased risk of epidural or operative delivery.
Indications for IOL
- Prolonged pregnancy
- Pre-eclampsia
- Pregnancy induced hypertension
- Pre-labour rupture of membranes
- Intrauterine growth restriction
- Diabetes, kidney disease
- Chorioamnionitis
- Intrauterine fetal death
Contraindications to IOL
- Placenta praevia
- Vasa praevia
- Malposition of the baby
- Cord prolapse
- Active primary genital herpes
- Previous myomectomy or uterine surgery
- Advanced cervical cancer
Is your body ready for childbirth?
IOL is not recommended before 39 weeks of gestation, unless there is a serious medical reason for the mother or her baby. At the end of pregnancy, as your body prepares for childbirth the cervix begins to change gradually: it becomes softer, thinner and opens (expands); these changes of the cervix is assessed by vaginal examination and depending on the findings of the vaginal examination, the Bishop score is determined, which shows how ready your body is for vaginal delivery. The Bishop score is a number from 0 to 13, and the higher the number, the more “ready” your body is for a normal birth.
- A score above 8 means that your cervix is mature and ready. Childbirth is likely to begin soon. If your labour needs to be induced, the success rate of vaginal birth are high.
- Score 6-7. There can be no reliable prediction of either the success of the challenge or the likelihood of vaginal delivery.
- Score below 6. The cervix is not ready enough for childbirth. In these cases the IOL process could last longer and the chances of failure are higher.
What are the differences between the IOL and spontaneous labour?
In most cases the IOL leads to a normal birth, however there are 2 differences in relation to spontaneous labour. Firstly, the duration of induced labour is significantly longer. A recent study estimated that the total labour time in nulliparous women was almost 50% longer in case of induced labour (20 hours in induction, 14 hours in spontaneous onset). Furthermore, the pain in childbirth following IOL is more intense and the need for epidural anesthesia is greater.
IOL process
Before the IOL commences, the midwife will perform a short tracing of your baby’s heart rate, known as a cardiotocograph ( ‘CTG’) and then you will be examined internally to ensure that your cervix (i.e. the neck of the womb) is ready for the induction process and that induction will be safe.
There are two ways in which your labour may be induced:
- Prostin tablets
For most women a tablet is inserted into the vagina and behind the cervix. This contains an artificial version of the hormone naturally produced by your body in labour. Your midwife will then monitor your baby for a further period of time. After this is completed you will be encouraged to mobilise (go for a walk or perhaps use a birthing ball), helping to promote a change in your cervix as you would in labour. As required, this process may be repeated up to two times with intervals of six hours in between. If your waters have already broken, just one tablet would be used in order to try and encourage your body to go into labour.
- Propess pessary
A controlled-release pessary inserted into your vagina, which can take 24 hours to work. If you do not have any contractions after 24 hours, you may be offered another dose.
For some women the use of these hormone tablets is not appropriate, and your doctor will have discussed this with you prior to your appointment for induction. If this is the case, a cervical ripening balloon (CRB) will be used instead. Your midwife will monitor your baby prior to the doctor inserting a very small deflated balloon into your cervix. This is then filled with water in order to encourage your cervix to dilate. The monitoring of your baby will continue for some time following the insertion of the balloon and you will then be encouraged to mobilise. The balloon is then removed 12 hours later when your doctor will perform an internal examination to assess whether there has been any change to your cervix. If, on examining your cervix, the obstetrician finds it has dilated but labour has not yet begun, the next step in the process will be to have the membranes around your baby broken artificially.
Sometimes, after breaking your waters by your obstetrician, a hormone drip is required to speed up your labour, which is called oxytocin. When the oxytocin drip is commenced, your baby’s heartbeat has to be monitored continuously on the CTG to make ensure he/she is not in distressed. Your doctor will discuss the options of pain relief you may want throughout labour.
You will be then examined 4 hours from regular contractions or within 6 hours from starting the hormone drip if you are not contracting.
Risks and benefits
If you are being induced because either you or your baby are (or may become) unwell, the specific risks of induction will be discussed with you when booking the induction. There are some general risks you should be aware of:
- Mobility – we try to encourage mobility throughout the induction process, however it may become necessary to record your baby’s heart rate continually during labour and the equipment used to do this may limit your ability to move around freely.
- Hyperstimulation – this is when the womb is stimulated and contracting too much, and the baby becomes distressed. This is slightly more common in IOL than in spontaneous labour, but can be easily treated with medicines. Your baby’s heart rate will be continually monitored to check for this
- Failed induction – some women do not respond to the IOL process. If, after a full course of cervical tablets, it is still not possible to break your waters, your obstetrician will discuss your options with you. These may include waiting for labour to begin spontaneously, further insertion of cervical tablets following 24 hour break (rest day) or caesarean section.
What are the differences between the challenge and the birth that starts automatically?
In most cases the challenge leads to a normal birth. But there are 2 differences in relation to the birth that starts automatically:
The duration of labor when provoked is significantly longer. A recent study estimated that the total birth time in firstborns was almost 50% longer in case of challenge (20 hours in challenge, 14 hours in automatic onset). The pain in childbirth after challenge is more intense and the need for epidural anesthesia greater.
How effective is induction of labour
The chance of a normal birth, when there are the right indications and conditions, is about 75% in women who give birth for the first time. However, sometimes IOL fails, therefore in these cases it is necessary to complete the delivery by caesarean section.
The IOL is slightly more likely to fail if when:
- This is your first childbirth (firstborn).
- The cervix is not ready and the Bishop score is low.
- The pregnancy is less than 39 weeks.
