Jun 311 min read

13 Reasons To Avoid Pethidine, Diamorphine And Other Opioids For Labour Pain Relief

Written by Bernadett Kasza, Birth Professional

Bernadett is a birth professional and the founder of Womanly Art of Birth. Her vision is to nurture the future of humanity, one birth at a time. Through her work, she helped numerous women and families to have healthy pregnancies and own their desired births and anxiety-free parenthood.

Labour pain and pain-relieving options are hot topics for expecting mums and families. While opioids are well-known choices, it's crucial to understand how they work before making a decision. This article delves into the effects of opioids on the body, blending medical research with maternal experiences to present 13 compelling reasons why you might want to avoid using them for labour pain relief.

Tom Saros Photography

What are opioids?

Opiates are naturally derived from poppy seeds, like morphine and opium. Opioids are the synthetically created version of this sedative compound.

After administration, opioids travel through the bloodstream and bind to the opioid receptors of brain cells. They bind to the same site where endogenous (your own, innate) opioids, like endorphins, bind.

There are many different brands available across the globe. Synthetic opioid brands like Demerol, Stadol, Nubain, Fentanyl, or naturally derived morphine are offered to women and birthing people during childbirth. Which brand is used depends on the country and the hospital where you plan to give birth. Opioids may be referred to under their generic names like morphine, diamorphine, pethidine, codeine and so on.

To learn more about which opioids are used in your country, visit the relevant medicinal regulatory body’s website in your country. In the UK it is the British National Formulary.

How do opioids work?

They reduce the awareness of pain and have a sedative effect on people. The impact of this type of analgesia varies greatly for everyone. Opioids do not take labour pain away completely.

Women’s experiences are significantly different from one another. Some report that it helped them relax, while others report not remembering their labour during the effect of opioids. Most women report a complete loss of control over their bodies with the backlash of still feeling pain.

The actual pain-relieving effect of opioid analgesia is extremely debatable and there is no unified research outcome that states undisputed high effectiveness for labour pain management. This is not surprising given the biochemical behaviour of opioids.

One of the concerning issues with having opioid pain relief is that when the effect of the drug wears off, pain sensitivity often increases. This phenomenon is called opioid-induced hyperalgesia.

How is it administered?

It can be administered as an intramuscular injection (with a long needle so it is delivered deep into the muscles), intravenous (via a drip that is inserted into your vein), epidural and intrathecal (they both are introduced via a needle into different parts of your spinal column). Also, it can be oral (tablet to swallow), buccal (tablet to be absorbed in the mouth), and transdermal (via a patch placed on the skin).

13 reasons to avoid using opioid painkillers during labour

1. Opioid concentration is higher in the foetus than in the mother

Opioids cross into the placenta thus into the baby in about 7 minutes after the administration of the drug. The more fat-soluble the drug is, the faster the drug crosses into the placenta and hence into the baby.

Why is it a problem?

Babies in the womb have a lower pH value thus drugs like pethidine get ionized in the foetus’ blood which further decreases their pH level. Due to the above, opioid drugs can get trapped in the foetus and cannot return to maternal circulation (drugs only cross the placenta when they are non-ionized).

The problem with lowered blood pH is that it causes foetal distress. Foetal distress and foetal acidosis mean that the birth of the baby should be imminent. Naturally, this depends on the level of acidosis, the progress of labour and the baby’s heart rate therefore it can easily become a time-sensitive matter that can lead to instrumental (forceps or vacuum), or operative delivery (caesarean-section).

This problem is also concerning due to their immature liver enzymes which make them excrete opioids slower than adults, in utero and after birth.

Until the drug gets metabolised by the baby’s system, the opioid affects them. This metabolisation can take up to 60 hours!

2. Opioids depress the central nervous system in both babies and adults

The Central Nervous System (CNS) is the brain and spinal cord. The CNS controls our vital functions such as breathing, heart rate, body temperature, movements, thoughts and emotions, hormone secretion, reflexive responses, sight and sense of smell. Read more about the CNS.

By the depressive effect of opioids on the CNS the following problems often occur in newborn babies. Decreased level of arousal, sleepiness, low muscle tone, compromised thermoregulation, abnormal reflexes, breathing problems and so on.

3. Opioid’s impact on feeding

The suppression of rooting reflexes and a delay in latching onto the breast due to sleepiness and depressed motor functions interfere with successfully establishing breastfeeding. It is normal and common to have a very sleepy newborn when mum has had opioids for pain relief. Further concern arises if the baby cannot be woken up for a longer stretch of time to feed, whether it’s breastmilk or formula thus they face a slower elimination rate of the opioids and consequently the drug remains in the infant's system for longer.

4. Breathing concerns in neonates

Depression of the CNS reduces their respiratory reflexes to cope with hypoxia and birth, thus their spontaneous breathing reflexes may fail upon birth and they may need resuscitation.

5. Decrease in body temperature

By the action of the opioids on the hypothalamus, the set point of the normal temperature range lowers therefore impairing thermoregulation (maintaining internal body temperature).

Additionally, hypoxia further reduces their ability to thermoregulate via nonshivering thermogenesis (NST), breaking down brown fat tissues.

This exacerbates the significant temperature change when leaving the warmth of the womb for a cooler environment. Newborns must be closely monitored to prevent excessive heat loss. Cold stress can be dangerous and may require admission to intensive neonatal care units.

6. Slow heart rate and fetal distress

Opioids can cause bradycardia in both the mother and the baby. The fall in maternal blood pressure and heart rate impacts placental perfusion. Perfusion means the transfer of blood, fluid and nutrients through a microcirculatory network. Sufficient placental perfusion allows the transport of oxygen, nutrients and waste products through the placenta to and from the mother and fetus.

The fact that opioids impact placental perfusion means that less oxygen gets to the baby and it increases the risk of acidosis as already mentioned before.

Low foetal heart rate (bradycardia) that lasts beyond 8 minutes shows significant foetal distress that triggers medical interventions. Opioids can easily tip your labour into an instrumental or operative birth that poses further concern for your and your baby’s health and the way they start their life.

More research is required to further analyse connections between opioid analgesia during labour and the risk of addiction in adult offspring in later life.

Opioid analgesia during labour is far from beneficial for your baby. All of the concerns listed above have several damaging effects on their overall health and can lead to intensive neonatal care admission.

Understanding the impact of opioids on babies is crucial and it's equally important to consider their effects on the birthing person. How opioids affect the mother's well-being and recovery is a significant part of the equation.

Let’s explore how opioids influence women during and after birth, shedding light on the broader implications of opioid use.

7. Challenges to cope with labour

As opioids have a sedative effect on the CNS, experiences such as dysphoria, euphoria, hallucinations, restlessness, delirium, visual disturbance, convulsions, muscle spasms, drowsiness, mental clouding and nightmares can occur since opioids interact with more than one type of receptors in the brain.

Women often fall asleep upon receiving opioids. This can make coping with labour pain more difficult. This might sound contradictory as opioids are classed as painkillers but what we shouldn’t forget is that they have a sedative effect and will not take all labour pain away.

The very fact that it depresses the CNS often takes away women’s and birthing people’s ability to cope with labour.

8. Longer labour

Opioids act on the posterior pituitary gland. This gland is responsible for the release of oxytocin. Oxytocin is crucial during labour as it causes the uterus to contract. As a result of the opioid's action, the length of both the first and second stages is linked to the amount of pethidine received during the first stage of labour. Also, we need to factor in that sedated women are less able to push. Prolonged labour can result in foetal distress, c-section or ventouse/forceps delivery, infections and postpartum haemorrhage.

9. Blocked maternal “instincts”

Oxytocin also plays a vital role in all ejaculative reflexes (milk let-down, orgasms and birth) and maternal behaviour. Oxytocin is known as the bonding and love hormone. Since opioids disrupt oxytocin release, they can also influence maternal behaviour and bonding. Studies have shown that opioid use during labour can disturb maternal coping and adaptation up to 6 months postpartum.

10. Breastfeeding issues

Generally speaking, babies born after opiated labour will be drowsy and sleepy, this in itself is a huge challenge in establishing breastfeeding. Coupled with maternal drowsiness and reduced oxytocin release, this puts both mothers and babies at a disadvantage from the start. I imagine it comes as no surprise that opioids cross into the breastmilk also.

11. Adult respiratory depression

It reduces the normal drive to breathe which requires close monitoring because respiratory acidosis and hypoxia can happen for mothers too (30 minutes after receiving the drug and can last up to 24 hours).

12. Bradycardia and hypotension in mothers

This fall in blood pressure (BP) and heart rate may cause light-headedness, feeling faint, or loss of balance. Blood pressure could fall 20% below the person’s average measurement.

13. Impaired mobility

Due to the sedative and muscle-relaxing effects of opioids, the labouring person will be spending more time in bed, lying down. This can have a negative impact on the baby’s journey through the birth canal in the form of labour dystocia (LD). Labour dystocia is an overall term for obstructions, making the birthing process slower and is generally the reason behind the ‘failure to progress’. From slow dilation of the cervix to shoulder dystocia, LD can be caused by malposition of the baby or impaired uterine contractions. Staying active during labour helps women cope with its challenges and push more effectively compared to lying down.

Other common side effects of opioid analgesia are nausea and vomiting, strong itchiness, excessive sweating, skin rash and water retention.

In this article, I focused on the direct effects of opioids on maternal, foetal and newborn physiology in healthy women and babies. Due to the nature of opioids, their administration must be done with extreme caution and are often contraindicated in the presence of certain pre-existing health conditions. It is important to note that opioids also interact with many other medications.

The dose, type, route, and timing of opioid administration during labour influence the severity of the issues listed above.

It is important to weigh up the risks and benefits when choosing pain relief and coping strategies for childbirth. Comparing the debatable effectiveness of opioid pain relievers and the extreme variety of maternal experiences to the numerous negative effects on you and your baby’s health, relying on opioids to provide safe and effective pain relief might not be the best choice.

Positive birth experiences do not correlate with pain-free labour and birth

Labour pain perception is different for everyone. Some women report no pain but ecstatic birth experiences, while others experience extreme pain. Pain perception and maternal satisfaction of birth are individual and are influenced by many factors. For example, the environment in which they give birth , how supported, respected, and listened to they feel during childbirth; their position, and the coping strategies they have learned during their pregnancy, and so on.

Maternal satisfaction with the birth experience does not depend on how pain-free their labour was. This qualitative study beautifully reflects maternal voices, and how positive, confident and strong they felt upon conquering labour pain.

We are all unique individuals thus the institutional ’one size fits all’ approach cannot provide sufficient care to everyone’s unique bio-psycho-social environmental and spiritual makeup.

You are unique and so is your birth experience. Contact me for personalised support to achieve the birth experience of your desire.

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Read more from Bernadett Kasza

Bernadett Kasza, Birth Professional

Bernadett is a Doula, Hypnobirthing Therapist, Antenatal Educator, Biomechanics for Birth Practitioner and Belly Dance Teacher.

Since 2011, she has been providing information and support to her perinatal clientele, actively championing their rights and wishes in the birthing room.

After her Midwifery studies, she left the profession to create a better educational and support system for women and their families. She has an impeccable record of getting her clients the birth they wish for.

By merging her social and scientific studies, Bernadett provides unparalleled services to families.

An hour-long Hungarian documentary (New Paths in The World of Birth) delves into her life and ground-breaking work in the field of birthing.

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