Drugs in labour and birth
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Amma Kyei-Mensah

Consultant in Obstetrics and Gynaecology. Lead obstetrician in maternal medicine at The Whittington Hospital in London.
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Birth and Labour

What are the pros and cons for having an induction?

Induction of labour has an impact on a woman’s labour and birth experience. It should be employed only as a medical necessity. Induced labour may be more painful than spontaneous labour, and epidural analgesia and assisted delivery are more likely to be required.
In Short

Reasons for induction of labour including: Prevention of prolonged pregnancy over 42 weeks gestation

Prevention of prolonged pregnancy over 42 weeks gestation

Medical reasons e.g. pre-eclampsia, gestational diabetes

Foetal reasons e.g. reduced foetal movements, poor growth of the baby

Ruptured membranes after 34 weeks gestation with no evidence of labour

No sign of labour after 24 hours with ruptured membranes at term or earlier

Mothers aged 40 years or over have increased stillbirth risk after 40 weeks

Mother carries Group B Strep with ruptured membranes at term*

*Induction may be offered before 24 hours

Bishop score

Your midwife or the doctors use the Bishop Score as a way of assessing the readiness of your body to respond to induction. The assessment involves an internal examination to feel the cervix (neck of the womb) and assess its “ripeness”.

A ripe cervix is soft, short, 2 or more cm dilated and is felt easily on examination. A ripe cervix scores more than 6 out of 10.

An unripe cervix is firm, more than 2 cm long, closed and cannot be easily felt. An unripe cervix scores less than 5 out of 10.

Induction succeeds more readily when the cervix is ripe.

Membrane sweeping

Also known as “a cervical sweep”.

This is an aid to inducing labour rather than an actual method of induction.

A cervical sweep can encourage spontaneous labour in a woman whose cervix is beginning to ripen in late pregnancy. The cervix should be soft and slightly open. It may be suggested by your midwife when you reach term i.e. your due date at 40 weeks gestation. Doctors may suggest sweeps from 37 weeks gestation if there are medical reasons to encourage spontaneous labour.

Membrane sweeping involves passing a finger through the cervix to gently lift the membranes from the wall of the uterus just above the cervix. If the cervix is closed, massaging around the cervix high up in the vagina may achieve a similar effect.

You can request several sweeps after 40 weeks to encourage the onset of natural labour. The mucus plug is usually dislodged from the cervix by a sweep so it is normal to have a show afterwards i.e. passing blood-flecked mucus from the vagina. A sweep should not cause heavy bleeding.

Evidence does suggest that with first-time mums it does take 2-3 cervical sweeps to get labour going. Sweeps are more effective when women are showing early signs of labour. Cervical sweeps can be offered from 39-40 weeks gestation with your consent. Cervical sweeps can be performed either in a hospital or a community setting.

Can I still have a Birth Centre delivery if I am induced?

If you have had an uncomplicated pregnancy with no medical or foetal reason for the induction you may be able to transfer to the Birth Centre once labour starts if that was your original plan. The cut off for Birth Centre labours is usually term + 13 days.

Methods of induction
Induction by use of prostaglandins

Prostaglandins are hormones produced in the uterus. They are responsible for period pains in the non-pregnant woman and for the ripening of the cervix and onset of labour in a pregnant woman.

This is the preferred method of induction; prostaglandin can be given as a gel, tablet or controlled-release pessary in hospital.

When you arrive on the antenatal ward, your baby will be monitored for a short time to check that all is well. You will be advised to pass urine to empty your bladder.

The midwife will examine you internally to assess the Bishop score and this will determine the prostaglandin dose that you receive. The prostaglandin is inserted high into the vagina to stimulate softening and dilation of the cervix. Your baby will be monitored again for 20 minutes after insertion.

If you receive the gel or tablet form, you will be reassessed after 6 hours. If the cervix is still not ripe and you are not contracting, another dose of prostaglandin may be suggested. If a controlled-release pessary has been inserted, you will be reassessed after 24 hours.

If you are a low-risk patient and your obstetric unit provides Outpatient Induction, you may be allowed home after a short period of observation with instructions to return for assessment at a specified time if labour has not started.

All forms of prostaglandin can occasionally cause strong contractions after insertion. This is commoner in women who have had several babies and is called hyperstimulation. Medication to relax the uterus is prescribed for women who have received prostaglandin tablets or gel. The controlled-release pessary can simply be removed.

Induction by use of mechanical dilators

These methods are gaining popularity as more women have had a caesarean section and wish to attempt vaginal birth after caesarean (VBAC). Use of prostaglandins or Syntocinon can increase the risk of uterine rupture so mechanical dilators such as Cook’s balloon and Dilapan-S avoid that risk.

These devices are inserted into the cervix. The Cook’s balloon is gently inflated in the cervical canal and Dilapan-S is a small rod containing a hydrogel which absorbs fluid when placed in the cervical canal. The resulting mechanical stretch stimulates the release of prostaglandins in the cervix which leads to softening and dilation.

Induction by rupturing the membranes

If the prostaglandin softens the cervix so that the membranes can be felt by the midwife on vaginal examination, she may discuss the option of artificial rupture of the membranes (ARM) of the amniotic sac. You would normally be transferred to a labour ward room for this. ARM involves inserting a slender plastic hook into the vagina and through the cervix to pierce the membranes. ARM is easier if the cervix is very ripe. It can be uncomfortable and if so Entonox (a 50:50 mixture of oxygen and nitrous oxide) may be offered as pain relief. You may experience a slight “popping” sensation followed by warmth as the fluid begins to drain out. The fluid usually looks clear, slightly yellowish or pink. Close surveillance or medical review may be needed if the fluid is green as this can suggest your baby is distressed as they green tinge is because they have pooed in the amniotic fluid.

Once the membranes are ruptured, the risk of infection increases over time as vaginal microorganisms can now reach the uterus more easily. This is why ARM is recommended in early labour rather than as a first-line method of induction.

IV Syntocinon during induction

Oxytocin is a hormone produced by the pituitary gland; it is responsible for uterine contractions. Syntocinon is an artificial form of oxytocin. It is not a first-line induction agent but is used to bring on contractions after ARM if spontaneous contractions have not started within 2 hours.

Syntocinon is administered intravenously via a small tube or cannula usually in a forearm vein. The resulting uterine contractions quickly become stronger and more frequent so this usually hurts more than natural labour. The drug is dripped into the vein at a set rate which is slowly increased depending on the frequency of contractions. The aim is for the uterus to contract 3 – 4 times in 10 minutes to cause gradual dilatation of the cervix at 1 cm per hour.

In most obstetric units an epidural will be offered before starting Syntocinon. Using Syntocinon after ARM will bring forward the time of birth but does not itself influence the mode of delivery.

Pain relief in induced birth

Induced labours can take a long time to become established and are often more intense than a spontaneous labour. You may need to reconsider your chosen pain relief options in your birth plan. If you respond to prostaglandin alone, further intervention may not be necessary as you become established in labour. Simple methods with no drugs such as breathing and relaxation exercises, massage techniques carried out by your partner, TENS in the earliest stages and use of water if there are no medical reasons to prevent it, can all be used successfully.

If the pain is more intense you may need to consider medication.

Entonox

Entonox is a 50:50 mixture of oxygen and nitrous oxide. It is inhaled via a tube or face mask to reduce the pain of contractions. It is effective but can cause nausea and lightheadedness. It is often more useful late in labour.

Opioids

These are strong painkillers and include pethidine and diamorphine. They provided limited pain relief during labour and can cause significant drowsiness, nausea and vomiting. Your baby may have short-lived respiratory depression and drowsiness which may last several days. They can also make it more difficult for your baby to breastfeed for the first 24-36 hours.

Epidural

Epidural pain relief is provided by the labour ward anaesthetist. A small tube (cannula) is inserted into a forearm vein to deliver intravenous fluids via a drip, Another small tube (epidural catheter) is inserted between the bones of the lower back into the epidural space which contains cerebrospinal fluid. A dose of local anaesthetic and often opioids is injected into the epidural space and this reduces contraction pain. The sensation is reduced over the abdomen and often the thighs. Top-up doses can be given by the midwife during labour to maintain an effective level of pain relief.

  • Provides more effective pain relief than opioids alone.
  • Not associated with long‑term backache.
  • Not associated with a longer first stage of labour or an increased chance of a caesarean birth.
  • It is associated with a longer second stage of labour and an increased chance of vaginal instrumental birth.
  • Can limit mobility. The aim is to establish a “mobile epidural” where the legs retain their strength whilst achieving good pain relief. Movement and adoption of active birthing positions will still be encouraged by your midwife if your legs remain strong.
  • You may suffer from a headache and nausea
  • Your blood pressure will be monitored frequently as can suddenly drop after epidural top-ups
Induction and caesarean rates

Caesarean rates with induction are greatly influenced by:-

  • The ripeness of the cervix
  • The reason for the induction

Successful induction is more common if the cervix is ripe with a Bishop score of 7 or higher.

Caesarean section is more likely if foetal compromise is the reason for induction as the baby may have less reserve to tolerate labour. Similarly, maternal illness such as pre-eclampsia will increase the risk of caesarean section.

Women having their first baby have up to a 50% chance of caesarean section.

Women who have had a baby before have a much lower risk of caesarean section after induction although the caesarean rate is higher than if they went into spontaneous labour.

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DISCLAIMER
This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Essential Parent has used all reasonable care in compiling the information from leading experts and institutions but makes no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details click here.