What to know about how pethidine and diamorphine work, their effects, and how to make informed decisions about pain management during labour.
Every woman and birthing person has the right to understand and access different pain management options during labour, including using opioids, such as pethidine and diamorphine.
A woman or birthing person must give informed consent before a midwife or doctor can provide any medicine or treatment. No one else can give consent on their behalf (not even a partner). Health professionals must listen and consider individual needs. They need to explain what is being given, what other options are available, and any possible side effects (Thompson, 2019).
This is so women and birthing parents are always involved in decisions about their care, their body, and their baby.
Want to find out more about pain management options and informed consent? We cover these topics in our NCT Antenatal Courses.
What are opioids?
Opioids are strong pain medicines usually given by injection in the thigh or buttock during labour. An anti-sickness medication may be given at the same time (OAA, 2025; NICE, 2025).
They are designed to help women and birthing people to feel relaxed and to get more rest or feel less worried about the intensity of labour (NICE, 2023, NHS 2023). Opioids can dull the sensation of contractions, but do not mask pain completely.
The most common opioid used during labour is pethidine (PEH-thi-deen). Diamorphine (DYE-uh-mor-feen) may also be used but less frequently (NHS, 2023). Around one in four women decide to use opioids for pain management during labour (Sprawson, 2017).
How does pethidine or diamorphine work?
After the injection, it takes about 20 minutes for pethidine or diamorphine to start working (NHS, 2023).
Some women and birthing people prefer to start with the smallest dose to see what the effects might be, as they can last between two and four hours (NHS, 2023). It is possible to have more than one dose if needed.
Opioids cross into the placenta, reaching their highest levels in the baby’s blood two to three hours after the injection (Fortescue & Wee, 2005). Because of this, they are not recommended in the final few hours before birth.
Find out more about the side effects of pethidine and diamorphine.
Who can have pethidine or diamorphine?
Anyone can ask for pethidine or diamorphine, but there may be medical reasons why they are not suitable, such as high blood pressure (Fortescue & Wee, 2005) or a previous bad reaction to opioids. A fear of needles may also be a factor.
Where can pethidine and diamorphine be given?
Opioids should be available in all birth settings (NICE, 2025), subject to local availability.
Some midwives who are working outside hospital settings may be cautious about using opioids because of their impact on babies. Parents planning a home birth should ask about this during pregnancy.
Women and birthing people cannot labour in water or have a water birth while under the effects of pethidine and diamorphine. After about two hours, once drowsiness has passed, it is usually safe to return to the birthing pool (NICE, 2007).
When can pethidine and diamorphine be given?
Pethidine and diamorphine are recommended only in early labour. They are not given if the baby is expected within three to four hours, to allow time for the medicine to wear off (NHS, 2023).
How effective are pethidine and diamorphine?
The National Institute for Health and Care Excellence (NICE) guidelines say healthcare professionals must inform women and birthing people that opioids will provide 'limited pain relief during labour and may have significant side effects' for both themselves and their baby (NICE, 2025).
However, opioids are commonly used possibly because they are well known, easily available, easy to administer, and inexpensive (Sprawson, 2017).
Studies have found women still report strong pain levels after being given opioids, and often ask for further pain management (Sprawson, 2017).
In one study of 80 women, experiences were mixed (Moran et al, 2019). Some felt pethidine helped, especially when used with gas and air (Entonox). While half said it did not relieve their pain, saying they could ‘feel everything’ and it had made ‘no difference’ to the intensity of their contractions.
Are there any side effects of pethidine or diamorphine?
There are side effects to using pethidine or diamorphine. In one study, some women described the feeling as similar to drinking a lot of alcohol. They said it made them so sleepy they couldn’t stay awake. This can make it harder for women and birthing people to make informed decisions, take part in their care, move around, or get into certain positions during labour (Sprawson, 2017).
Women in this study also reported:
- Feeling sick or vomiting
- Feeling very drowsy and unable to move around
- Difficulty concentrating or focusing
- Feeling disconnected from their labour and unable to process what was going on around them
- A negative impact on their memories of labour and childbirth
Other studies have highlighted additional effects on women and birthing people, including (Fortescue & Wee, 2005):
- Confusion, loss of control, and sleepiness
- Slowed breathing, which may mean oxygen is given through a face mask and monitoring could be needed. Although this is rare with doses used in labour (OAA, 2025)
- Slower stomach emptying, which can be a problem if a general anaesthetic is needed
- Involuntary muscle spasms
Are there any side effects for the baby?
After the injection, opioids cross the placenta, and babies cannot easily process them. This is why they are recommended to be used earlier in labour, when they can be metabolised by the mother or birthing parent’s system (Fortescue & Wee, 2005). However, the timing of a baby’s birth can be hard to judge.
Research shows babies may be sleepier, less attentive or alert, and less able to establish breastfeeding or chestfeeding. These effects can last for several days (NICE, 2023; Fortescue & Wee, 2005; Hemati et al, 2018).
If given too close to birth, opioids may also affect a baby’s breathing, which can sometimes mean the baby needs support in a neonatal unit. If this happens, another medicine, called Naxolone, can be used to reverse the effects of the opioids (OAA, 2025; NHS, 2023).
Researchers say there are gaps in understanding the longer-term effects of opioids and have called for more investigation into their impact beyond the first few days after birth (Sprawson, 2017).
What other pain management options are available?
To learn about other pain management options read our articles on:
Need more information?
Everyone woman and birthing person has the right to feel safe, informed, supported, and confident about their decisions.
For further information, we offer NCT Antenatal Courses, which are a great way to find out more about labour, birth, and the early days with a new baby.
Our NCT support line also offers practical and emotional support with feeding your baby and general enquiries for parents, members and volunteers: 0300 330 0700.
Fortescue C, Wee M. (2005) Analgesia in labour: non-regional techniques. BJA Educ. 5(1):9-13. https://doi.org/10.1093/bjaceaccp/mki002
Hemati Z, Abdollahi M, Broumand S, Delaram M, Namnabati M, Kiani D. (2018) Association between newborns' breastfeeding behaviors in the first two hours after birth and drugs used for their mothers in labor. Iran J Child Neurol.12(2):33-40. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5904736/ [Oct 25]
NHS (2023) Pain Relief in Labour https://www.nhs.uk/pregnancy/labour-and-birth/pain-relief-in-labour/ [Oct 25]
NICE (2025) Intrapartum Care Guidelines Overview | Intrapartum care | Guidance | NICE https://www.nice.org.uk/guidance/ng235 [Oct 25]
OAA (2025) Opioids - Labour Pains https://www.labourpains.org/during-labour/opioids [Oct 25]
Sprawson, E. (2017). Pain in labour and the intrapartum use of intramuscular opioids—how effective are they? British Journal of Midwifery, 25(7), 418–424. https://doi-org.apollo.worc.ac.uk/10.12968/bjom.2017.25.7.418
Thomson, G., Feeley, C., Moran, V.H. et al. Women’s experiences of pharmacological and non-pharmacological pain relief methods for labour and childbirth: a qualitative systematic review. Reprod Health 16, 71 (2019). https://doi.org/10.1186/s12978-019-0735-4
