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Labour pain relief: intramuscular opioids – pethidine and diamorphine

Opiates, like heroin, may not be what you'd expect to use in pregnancy or labour – but synthetically derived opioids like pethidine and diamorphine may have their place. Here, we explain all...

What are opioids?

Pethidine and diamorphine are opioids, medication derived and synthesised from the resin of the opium poppy.

Opioid drugs (OAA, 2019) are most useful in early labour (Lowth, no date). They aim to alter your mood during labour so you're more relaxed and can rest or sleep (Lowth, no date).

The most common type of opioids used during labour are pethidine or diamorphine, although some hospitals use other types (Lowth, no date; OAA, 2019). Hospitals generally offer one of these types of opioid, but you can ask if you’d prefer a different one.

Up to 25% of women in the UK use pethidine or a similar opioid during labour (Moran, 2019).

How are opioids like pethidine used?

A midwife would usually inject pethidine or diamorphine into your thigh muscle when you're in labour. These opioids take 20 to 30 minutes to work, and each injection lasts for two to four hours (Lowth, no date; OAA, 2019). Your midwife may repeat the dose after one to three hours if it isn't having enough effect (Lowth, no date)

You can also receive opioids orally or intravenously. You'll also be given an anti-sickness medication at the same time as an intravenous or intramuscular opioid (NICE, 2007).

Are opioids good for labour pain relief?

About one in four women use opioids during labour for pain relief (Lowth, no date). But while they’re commonly used, opioids are less effective than Entonox, and their long-term effects are unknown (Sprawson, 2017; OAA, 2019). The advantage of opioids is that they’re well known, easily available for midwives and inexpensive (Sprawson, 2017).

You'll start to feel the effects of the opioid after about half an hour and the pain relief may last a few hours (OAA, 2019). Nobody knows whether pethidine or diamorphine is better for pain relief, or which one women in labour are more satisfied with (Smith et al, 2018).

NICE guidelines describe intramuscular opioids as providing limited pain relief during labour, and may have significant side effects in the pregnant women (drowsiness, nausea and vomiting) and the baby (short-term respiratory depression and drowsiness which may last several days) (NICE, 2007).

Are opioids suitable for everyone?

Some women already know that they react poorly to opioids and so would avoid them.

Pethidine can induce involuntary muscle spasms, and so may not given to those women who have high blood pressure caused by their pregnancy (Fortescue&Wee, 2005).

Intramuscular opioid painkillers are available in hospitals and birth centres, and may be available for home births. So for a planned home birth, check with the midwife in advance if intramuscular opioids are available (Lowth, no date).

What are women’s experiences of pethidine or diamorphine?

Each woman responds in different way to opioids for labour pain. Some women find opioids help them feel more relaxed and less worried about the pain (OAA, 2019). Others find it disappointing as a pain reliever and feel less in control (Lowth, no date; OAA, 2019).

There isn't much good quality evidence that pethidine can alleviate labour pain for most women. When compared with a placebo, no clear differences were seen in maternal satisfaction with pain relief or the number of women requesting an epidural (Smith, 2018).

In trials, about half the women were happy with the pain relief obtained from pethidine (when used alongside other pain relief such as gas and air). But while some say it was "brilliant" and they "didn't feel a thing," about half reported that they could "feel everything" and it had made "no difference" to the intensity of their contractions (Moran, 2019). Some women likened the effects to heavy alcohol consumption (Moran, 2019) and some said it made them feel extremely sleepy.

What are the side effects of opioids like pethidine?

Side effects might include feeling woozy, sick or forgetful (NHS, 2017).  You might need oxygen if your breathing is affected (OAA, 2019). Opioids can also make you too drowsy to push effectively (Lowth, no date).

Some women reported feeling disconnected from their labour and unable to focus or process what was going on around them (Moran, 2019).

Are there any side effects for the baby?

Opioids cross the placenta and the baby cannot easily process them. So the most appropriate use is in early labour, when they can be processed by the mother's system (Lowth, no date). An additional dose will not be given if birth is anticipated within 3-4 hours. However, that is not easy to predict.

Opioids in your baby's system can affect the breathing after birth. This can mean your baby is transferred to the neonatal unit for help with breathing (NHS, 2017). Some NHS Trusts offer an opioid antidote called Naxolone to you and your baby if necessary (Lowth, no date) but there are concerns about a lack of benefits and long-term developmental problems for the baby in these cases (Moe-Byrne et al, 2018).  

Drugs such as pethidine cause decline in breathing and muscle functions, oxygen saturation, and the newborn heartbeat after birth. There have been reports of a direct link between the dose of used drugs in labour and the newborn’s sucking ability (Hemeti, 2018).  

Opioids can also make babies sleepy after birth, which can affect their normal instinctive behaviours. (Lowth, no date)

Is there any impact on labour?

Your carers will recommend you don't go into water (like a birthing pool or bath) within two hours of being given opioids or if you feel drowsy (NICE, 2007).

Intramuscular opioids could delay the stomach emptying, which might be a problem if you needed a general anaesthetic during labour (OAA, 2019).

They could slow down your breathing, which would mean you're given oxygen through a face mask and would need your oxygen levels monitored (OAA, 2019).

How do opioids during labour affect breastfeeding?

Pethidine, diamorphine and other opioids may interfere with breastfeeding (NICE, 2007; OAA, 2019)

Pethidine can have an adverse effect on a newborn's sucking ability and breastfeeding. It also affects the mother's level of the oxytocin hormone which may delay lactation (Hermati et al, 2018).

There’s also the risk that if you and your baby are separated because your baby goes to the neonatal unit, that interrupts bonding and hence affects breastfeeding (Lowth, no date; NHS, 2017; NICE, 2017).

Does having opioids during labour have any long-term effects?

There are no reported long-term effects.

Is there any impact on mental health?

Research showed that some women reported feeling out of control as they were dependent on the midwife to give them the drug, or they thought they didn't receive adequate support with breastfeeding because of having the drug (Thompson, 2019).

Some reported that the care providers became more distant after having this kind of pain relief, particularly when they weren't looked after by the same midwife or care provider throughout their labour. This might be a real substandard level of care, or it could be because of distorted perceptions due to the drug (Thompson, 2019).

Some women reported feeling disconnected from their labour and unable to focus or process what was going on around them (Moran, 2019). These experiences could lead to negative feelings about the experience of labour and birth.

What happens if I don’t like opioids?

If you decide you want to use an opioid, you can ask for the lowest possible dose to see how you react to it.  You can always have more but it takes two to four hours to wear off if you don’t like it.

Can midwives prescribe opioids such as pethidine?

Pethidine, diamorphine or other opioids are available in all birth settings (NICE, 2007). As midwives can administer opioids, they are widely available. Yet midwives who are caring for women in non-hospital environments, like at a home birth, might be cautious about using opioids because of their impact on babies.

When do women have pethidine during labour?

Pethidine or diamorphine tend to be offered early in established labour, for women who have had a long and tiring early labour.

Opioids should not be given too close to the birth because of the effect on the baby, though it’s difficult to know when that will be (Lowth, no date)

What can my birth partner do to help?

The birth partner can help the woman remain in a good position, comfortable, hydrated and emotionally supported.

Can I have pethidine (or other opioids) with other options?

If you’ve had opioids, you’ll be discouraged from using a birth pool until the drugs have worn off. You can use Entonox and TENS alongside opioids.

Would I need any additional procedures?

You’d be offered anti-sickness medicine at the same time as the opioid injection (Lowth, no date; NICE 2007).

Are there any alternatives?

Forms of opiates which may be offered as intramuscular injections during labour are pethidine, diamorphine, fentanyl and meptid (Lowth, no date).

While there is no national guidance, NCT practitioners have observed that oral morphine liquid may be offered in early labour – ask hospitals about this.

Remifentanil is an opioid which is administered via a drip and is controlled by the mother.

This page was last reviewed in March 2021.

Further information

Our support line offers practical and emotional support with feeding your baby and general enquiries for parents, members and volunteers: 0300 330 0700.

We also offer antenatal courses which are a great way to find out more about pregnancy and life with a new baby.

Research from the Royal College of Obstetricians and Gynaecologists (RCOG) about the use of water as pain relief in labour.

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