Induction and Augmentation of Labour

Induction of labour

Induction of labour

Augmentation of labour

Induction of Labour

What is induction of labour?

Induction of labour is the process of using drugs or other methods to artificially start labour. Induction is carried out so that a baby can be delivered even though labour has not started spontaneously (on its own).

How commonly is labor induced?

A quarter of all pregnant women in Australia have their labour induced.The most common reason for inducing labour is due to the baby not being born by a week or two after its due date (prolonged pregnancy).

Why may labour be induced?

In some cases, labour may be artificially started by the doctor or midwife, because the health of the mother or baby is at risk. Some examples of situations in which this may occur include:

the baby being very overdue (more than 11 days late);
the mother having high blood pressure (pre-eclampsia);
signs of infection;
the baby being distressed; and
the baby not growing correctly.

For induction to be considered, the risks of the procedure must be less than the risk to the mother or baby if the pregnancy is allowed to continue. There must also be no factors that make vaginal delivery unsuitable, such as active genital herpes, or a very large baby and a small mother. If such factors are present, a caesarian delivery is a more appropriate option than induction.

Induction works best for women who are at least 39 weeks into their pregnancy, and who have a ‘favourable' cervix. The cervix is the opening of the womb (uterus) into the vagina (birth canal). As a woman's body prepares for birth, the cervix becomes soft, and it begins to open (dilate) to allow the baby out. This process is known as ‘ripening' of the cervix. When the cervix is ‘ripe' (soft and opening) it is called a ‘favourable' cervix. A score known as a ‘Bishop's score' is used to measure how ripe the cervix is. A score of 7 or less is known as not favorable. A score of 8 or above is favourable and it is more likely the woman will respond well to induction.

How is labour induced?

Induction of labour If labour needs to be started, but the delivery of the baby is not urgent, induction may be considered. If the cervix is closed and hard (unfavourable: ‘Bishop's score' ≤ 7) the options for inducing labour include:

Gel: Prostaglandin gel is placed on the cervix, which causes it to get softer and start to dilate. Following use of the gel, the chance of delivery within 24 hours is increased. The likelihood a woman will require a Caesarean delivery is not changed. The gel can cause the uterus to contract, which is helpful to start labour. If the uterus is over stimulated (uterine hyper-stimulation), this can cause distress to the mother or baby, so monitoring using a CTG is important.
Foley catheter: a small tube is placed in the cervix and a balloon is inflated. When used to induce labour, the catheter is taped to the inner thigh, so the pressure of the balloon on the cervix acts like pressure of the baby's head, causing the cervix to ripen. Once the cervix is ripe, the balloon falls out. This method has a lower risk of causing hyperstimulation than the gel, and is useful when the woman is not able to tolerate drugs.

If the cervix is soft and starting to open (favourable: ‘Bishop's score' > 7), the options for inducing labour include:

‘Stretch and sweep', also known as membrane stripping: This is done to ‘bring on' spontaneous labour (contractions that start on their own without the need for drugs). The doctor or midwife inserts a gloved finger into the vagina, through the cervix (stretch), and then rotates it around the bottom of the womb to separate the membranes around the baby from the wall of the womb (sweep). It is usually used for women who are at term (more than 37 weeks into their labour - the baby's ‘due date' is at 40 weeks). This may be carried out weekly from 38 weeks onwards, and halves the number of babies born post-term (42 weeks and onwards). It may cause discomfort, some bleeding and irregular contractions. It is not dangerous for the baby, and reduces the need for other forms of labour induction.
Rupture of the membranes (amniotomy, artificial rupture of membranes): using a gloved finger, or a small hook which is passed though the cervix to ‘nick' the membranes surrounding the baby. This causes the ‘waters to break'. This procedure is not generally painful, but may be uncomfortable. On its own, artificially rupturing the membranes does not speed up labour, but in combination with other methods, such as oxytocin, it is helpful; and
Oxytocin (Syntocinon) drip: This drug causes the uterus to start to regularly contract (labour). If the cervix is not ripe, prostaglandins or a Foley catheter will be used first, before the drip is started. The membranes may also be artificially ruptured before the contractions are started with oxytocin. Once labour has started, the drip may be turned off. Monitoring with a CTG is used while the drip is up.

There are several other methods that have been suggested to ‘bring labour on'. These do not have good evidence that support their use, that is, their safety and effectiveness in pregnant women has not been proven. For this reason, none should be carried out without seeking advice first from a medical doctor. Such methods include:

Unprotected sex (the semen produced when a man ejaculates is thought to ripen the cervix);
Herbal supplements (eg raspberry leaf tea);
Acupuncture;
Castor oil;
Hot baths;
Enemas; and
Breast/nipple stimulation: causes the uterus to contract, and may be useful in starting labour within 72 hours if a woman already has a favourable cervix.

What are the risks of inducing labour?

The risk of induction of labour varies depending on how many weeks into the pregnancy the woman is, the reason for the induction, and how ripe the cervix is.

Due to the risk of induction outweighing the benefits, labour will not generally be induced under the following circumstances:

The woman has had an unusual type of caesarean section in the past, with a classical incision which is a cut in a vertical line down the middle of the abdomen (tummy);
Umbilical cord prolapse, where the cord connecting the baby to the placenta exits the womb before the baby;
Active genital herpes infection, where sores are present on the vagina;
Placenta praevia, where the placenta grows over the opening of the womb;
The head of the baby is known to be too large to fit through the pelvis of the woman;
The baby entering the birth canal is in the wrong position (malpresentation), such as the baby lying sideways (transverse or oblique lie), or the shoulder coming out first (shoulder presentation);
The mother refuses; or
The baby is significantly distressed, and may not be well enough to tolerate vaginal delivery.

In Australia, induction of labour for social reasons or for convenience of the doctor is not routine practice. This is due to the many risks associated with induction of labour, which must be justified by greater risk to the mother or baby should labour continue.

Risks of induction of labour include:

Increased likelihood of unplanned caesarean section (which has greater risks than planned/elective caesarean section), particularly for women having their first baby. If induction of labour fails (the cervix doesn't open enough and the baby can't be delivered), caesarean section is often required;
Increased cost overall compared with no induction of labour. This cost is largely related to increased rates of caesarian section;
Over-activity of the uterus may occur with the use of prostaglandins or oxytocin. Uterine hyper-stimulation occurs when there are more than five contractions in 10 minutes, contractions lasting at least two minutes, or contractions occurring within one minute of each other. There may or may not be changes to the baby's heart rate;
Increased likelihood of the mother bleeding after she delivers the baby (post partum haemorrhage), and increased risk of the baby being distressed during birth;
Increased risk of breathing problems in the infant, particularly if the baby is delivered before 39 weeks gestation;
Risks associated with amniotomy including introduction of infection, umbilical cord prolapse and bleeding. Accidental amniotomy may occur with membrane stripping; and
Nausea and vomiting are infrequently associated with use of oxytocin, and rarely, heart rhythm problems and allergic reactions may occur.

What are the advantages of inducing labour?

There is evidence that induction of labour in high risk groups can improve outcomes for a mother and her baby if it is appropriately timed. There is no clear evidence for which specific circumstances are best managed by induction.

Labour that is induced for medical reasons in pregnancies where the health of the baby or the mother is at risk has the following advantages:

There is an increased likelihood of delivery within 24 hours;
Reduces the frequency of post term delivery (greater than 42 weeks), which has been associated with higher rates of problems for the mother and baby, including birth of large babies and prolonged labour.
Reduced trauma to the infant at birth (vacuum or forceps injury);
Reduced rates of admission of the baby to the neonatal intensive care unit;and
Higher rates of uncomplicated vaginal delivery.

Reduction in stillbirth, which is more common when a baby is significantly overdue, has not been proven in studies investigating induction of labour.

Some proposed advantages of scheduled (planned) induction of labour include:

Minimising disruption to a pregnant woman's social and domestic responsibilities;
Avoidance of disruption to an obstetrician's work responsibilities, non-work related activities, and sleep;
Avoidance of delivery on the way to the hospital, particularly for women who live in isolated locations, or who have a history of very quick labour; and
Ensuring a woman's preferred obstetrician or midwife is available.

Augmentation of labour

What is augmentation of labour?

Augmentation of labour refers to the use of medication or other intervention to ‘speed up' the process of labour. Augmentation may be required to assist with an abnormal or difficult labour (dystocia), or to speed up normal labour if the health of the mother or baby is at risk. Augmentation usually involves artificially increasing the frequency or strength of contractions of the uterus, with or without artificial rupture of the membranes around the baby, change in position, instrumental delivery (forceps, vaccum) and other techniques. Once labour is established, regular assessment of how far down the birth canal the baby is, the dilation of the cervix, and the health of the mother and baby takes place to make sure labour is going well. Once the cervix is dilated to 4cm (active first stage), extra cervical dilation should occur at the rate of one centimetre per hour, or faster for women who have had children before. If this is not taking place, augmentation may be considered.

Why may labour be augmented?

Augmentation of labour Augmentation may be used to avoid problems with the mother or baby that may occur if labour lasts too long (prolonged labour). Such problems include the mother bleeding too much (postpartum haemorrhage), damage to the pelvic floor of the mother leading to problems like incontinence, respiratory problems with the baby, and the need for admission of the baby to the intensive care unit. Augmentation is a more conservative option for managing problems in labour than a non-elective caesarian delivery. Failure to progress as expected in labour may indicate augmentation is required, in an attempt to prevent the need for caesarian section.

What are the outcomes of augmentation?

Compared with women who have no problems with their vaginal delivery, women who have difficulties (dystocia) that require augmentation are more likely to:

require Caesarean and ventouse deliveries;
have non-clear amniotic fluid;
experience postpartum haemorrhage; and
deliver a baby with a low one-minute neonatal Apgar score.

How well the different methods of augmentation shorten the length of labour is discussed below.

More information on stages of labour

How is labour augmented?

First stage

Augmentation of labour The first stage of labour lasts from when labour starts until the cervix is fully dilated and the woman starts pushing the baby out. In the first part of first stage (0-4cm dilation of the cervix, known as latent phase), augmentation may take the form of therapeutic rest, or drugs that cause the uterus to contract. Prolonged first stage during labour is associated with a higher risk of caesarian delivery, and reduced health of the baby at birth (lower Apgar score).

Therapeutic rest involves the mother receiving injections of strong painkillers so she can rest or sleep with minimal discomfort while labour progresses. Occasionally sedatives are also prescribed. This option is not appropriate if delivery is urgently required due to signs of the mother or baby being unwell. Of women who are managed with therapeutic rest, 85% will wake up in the active phase of labour (4-10cm dilated), 10% are likely to be in false labour, and 5% have ongoing problems with their labour progressing.

Drugs that stimulate the uterus, such as oxytocin, may be used to help speed up labour from the latent (0-4cm dilated) to the active phase (4-10cm dilated) of first stage. Oxytocin is given into the veins via a drip, with the amount of drug increased or decreased depending on how the woman is responding. Oxytocin is not likely to be used when vaginal delivery is not safe, the uterus is not strong due to scarring, or other circumstances listed above. One study found that oxytocin and therapeutic rest are equally effective and safe options to manage prolonged latent phase. In one study, oxytocin took an average of 3.4 hours to move labour along into the active phase of first stage. Once the labour has reached the active phase, oxytocin is more effective in speeding up labour than rupturing membranes, walking around, or other measures. The use of oxytocin to augment labour is known to reduce the length of labour by hours, with no change in satisfaction of the mother, or harm to the mother or baby. Caesarean delivery rates are not affected.

Artificially rupturing the membranes around the baby does not reduce the length of the first stage of labour. Conservative measures such as walking around have been found to increase the comfort of labouring women, but do not have an effect in terms of speeding up prolonged labour.

If augmentation during first stage does not result in the labour progressing as expected (cervical dilation of at least 1cm per hour), caesarian delivery of the baby may be required.

Second stage

Image courtesy of Blausen Medical Communications. Contact Andrew Walbank.

Second stage is from the time the cervix is fully dilated and the woman is allowed to push, until the baby is delivered. Long second stage can be managed by continued observation (expectant management), operative vaginal delivery (forceps or vacuum), or caesarian delivery. The most appropriate option will depend on how the mother and baby are, signs of progress of delivery, and length of the second stage.

Artificial rupture of the membranes around the baby (amniotomy) is often performed during second stage if the membranes are still intact. Routine episiotomy (cutting the edge of the birth canal to make it wider) does not shorten the second stage of labour and is not useful for this purpose.

Successful vaginal delivery is the most common outcome of women who experience a long second stage. The most common problems with the baby due to prolonged second stage include intensive care admission and injury to the nerves in the neck that supply the arm. Long second stage is associated with increased harm to the mother including significant tears to the birth canal, infection of the uterus, and bleeding following birth (postpartum haemorrhage).

Long second stage may be augmented through the following techniques:

Treatment with an oxytocin (Syntocinon) drip which causes the uterus to contract;
Reducing the numbness and weakness that occurs with epidural or spinal anaesthetic, so the woman is better able to push. This reduces the length of second stage and the need for forceps or vacuum, although it results in more pain for the mother;
Continuous attendance of a support person to assist the mother;
Delayed pushing - if the baby's head is still not all the way down into the pelvis, the woman may delay pushing if she has no urge to do so;
Changing the position the woman has chosen to push (upright, kneeling on all fours, lateral position);
Instrumental delivery (forceps or vacuum). There is wide variability in the outcome with these techniques depending on why they were used and the skill of the doctor or midwife;
If there is failure of the methods outlined above, with signs of the baby being distressed, a non-elective caesarean delivery may be required.

More information

For more information on birth, including statistics, birthing types and stages of labour, as well as some useful animations, see Birth.

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