Induction and augmentation of labour are methods to facilitate the birth of a child under certain circumstances.

THERE are occasions when artificial starting of uterine contractions in an effort to achieve a vaginal birth is required. This is called induction of labour.

There are also occasions when labour, which has already started, needs to be given some assistance because it is not progressing, or it is progressing too slowly. This is called augmentation of labour; the word “augment” means “to make greater, increase, or more intense”.

Reasons for induction

Induction of labour is recommended if there are risks to maternal or foetal health.

Women with uncomplicated pregnancies are usually offered induction between 41 and 42 weeks of pregnancy (gestation) to avoid the risks of prolonged pregnancy, which include increased risk to foetal health or stillbirth.

There are no means available to detect the foetuses more likely to be affected by such risks. The exact timing takes into consideration individual preferences and local circumstances. If one decides not to have an induction, arrangements for increased monitoring of foetal well-being will be made.

Premature pre-term rupture of the membranes (PPROM) occurs occasionally. The maternal risks include infection and possible Caesarean section. The foetal risks include infection and the problems of premature birth. In general, induction is not carried out until after 34 weeks gestation unless there is evidence of infection or foetal compromise.

If labour has not started 24 hours after the membranes have ruptured after 37 weeks gestation, induction will usually be offered.

Induction will also be considered in maternal conditions like high blood pressure, poorly controlled diabetes, kidney disease and previous stillbirth, as well as foetal conditions like poor growth, too little amniotic fluid and foetal death.

Induction is not usually offered for those with previous Caesarean sections or breech presentation, or if there is suspicion that the foetus is large, unless there are reasons for not prolonging the pregnancy.

Induction is carried out for non-medical reasons in exceptional circumstances, like parental request or a mother living far away from a hospital. This is done only after 39 weeks gestation to reduce the risk of inducing a foetus whose lungs are not mature.

Reasons for augmentation

Augmentation is required if labour is abnormal, or normal labour needs to be speeded up because of maternal or foetal risks.

When the cervix reaches a dilatation of 4cm, subsequent dilatations are at a rate of 1cm per hour in a mother having her first baby, or faster in a mother who has given birth before. Augmentation will be considered if this is not occurring.

Augmentation is also considered when there is concern about the problems of prolonged labour, like maternal medical conditions, damage to mother’s pelvic floor, bleeding after delivery (postpartum haemorrhage), respiratory problems in the newborn, etc.

Cervical assessment

Changes in the cervix occur a few weeks before spontaneous labour begins. An assessment of the cervix will be done prior to an induction. The examination provides information about the readiness of the cervix for labour.

A system called the Bishop score based on the dilation, effacement (length), station, position and consistency of the cervix is used in this assessment. The score ranges from 0 to 12.

A score of 8 or more (“favourable cervix”) indicates that the likelihood of spontaneous labour or the response to induction is high. A score of less than 6 indicates that the cervix may not be ready for labour.

Membrane sweep

At the time of cervical assessment, a membrane sweep will be offered to help the mother go into spontaneous labour. This involves the insertion of a finger into the cervix and making a circular movement to separate the membranes from the inner lining of the uterus. If this is not possible, massaging the area around the cervix may achieve the same effect.

The foetal heart, which is checked before and after the membrane sweep, should have a normal pattern.

The membrane sweep may lead to some bleeding and/or discomfort.

A membrane sweep is usually offered at 40 to 41 weeks to a mother having her first baby, and at 41 weeks to a mother having her subsequent baby. Additional membrane sweeps can be carried out if spontaneous labour does not start.

Membrane sweep is considered an adjunct to, and not a method of, induction.

Medicines used to induce labour

Prostaglandin (PG) E2, which is available as a pessary, tablet or gel, is the preferred method, and is inserted into the vagina. One dose is inserted, followed by a second dose after six hours if labour has not been established.

Misoprostol, a PGE1 analogue used to prevent non-steroidal anti-inflammatory drug-induced (NSAID) stomach ulcers, is used in inducing labour when there is an intrauterine foetal death. It is taken orally or inserted vaginally.

Although unlicensed for induction of an uncomplicated pregnancy, it is used in many countries because it is much cheaper than PGE2.

Sometimes, an intravenous drip containing oxytocin is used to hasten up labour. Oxytocin is not used within six hours after insertion of PGE2 gel, or with PGE2 in situ, or within 30 minutes of its removal.

It may take some time for labour to start with induction, especially if the cervix is unfavourable. Once labour commences, it should proceed as in spontaneous labour.

Amniotomy

This is the breaking of the membranes with a hook-like device. It can start contractions, or it can make the contractions stronger if labour has already started.

It is not used as a main method of induction unless there is reason for not using medicines, eg an increased risk of uterine hyperstimulation.

Induced labour is usually more painful than spontaneous labour. Various methods of pain relief should be discussed prior to admission to the hospital. Planning in advance can help make the labour less painful.

It is recommended that there should be facilities available for electronic monitoring of the foetal heart and contractions during induction or augmentation.

A normal foetal heart rate pattern should be confirmed prior to the administration of medicines to the mother, after which, there should be continuous foetal heart monitoring.

When the foetal heart rate pattern is confirmed normal, intermittent checking of the foetal heart with a foetal stethoscope or an ultrasound may be used to monitor foetal well-being.

If the foetal heart rate pattern is abnormal, immediate steps should be taken to address the problem.

If induction fails, an assessment of the maternal and foetal conditions will be made. The doctor will recommend another induction or a planned Caesarean section depending on each mother’s individual condition.

The methods of augmentation in the first stage include intravenous oxytocin and adequate pain relief.

The methods of augmentation in the second stage include intravenous oxytocin, reducing the weakness and numbness of epidural or spinal analgesia, delay in pushing until the foetus is way down in the pelvis, the presence of a support person for the mother, and changing the mother’s position.

There is no scientific evidence to support the following as methods of induction – herbal supplements, homeopathy, castor oil, enemas, sexual intercourse, hot baths and acupuncture.

Provided there are medical reasons, induction and augmentation can be potentially life-saving. In the case of induction, labour can be pre-arranged for mother and doctor.

Risk assessment

The risk of prostaglandin and oxytocin induction is uterine hyperstimulation, which is defined as five or more contractions in 10 minutes in a period of 30 minutes, contractions lasting more than two minutes, or contractions of normal duration occurring within 60 seconds of each other.

There may or may not be foetal heart rate changes.

If not managed early, hyperstimulation leads to poor placental blood flow, resulting in decreased foetal oxygenation, foetal compromise, and even, foetal death.

Another risk is that of potentially life-threatening uterine rupture, especially in those with previous Caesarean section or uterine surgery.

Other risks include maternal and foetal infection; increased risk of foetal distress and unplanned Caesarean section, where risks are more than that of planned Caesarean section; increased risk of postpartum haemorrhage; increased risk of epidural analgesia and instrumental vaginal delivery; and increased risk of breathing problems in the newborn, especially if delivery occurs before 39 weeks gestation.

Medical problems prior to or during pregnancy may exacerbate these risks.

Discussion between mother and doctor about the benefits and risks of induction and/or augmentation, as well as the alternatives is essential. The doctor will make known the reasons for the intervention and provide information about the when, where and how of the intervention. Various methods of pain relief will be discussed.

It is vital to also discuss what the options are, should induction fail.

> Source: Dr Milton Lum