Pain relief in labour

Published on 09/03/2015 by admin

Filed under Obstetrics & Gynecology

Last modified 22/04/2025

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Chapter 41 Pain relief in labour

Michael Flynn

About two-thirds of women in labour consider the pain very severe and intolerable. There is a need for antenatal preparation, with balanced information and opportunity to discuss options of analgesia.

Pain in labour

Causes

• dilatation of the cervix
• contraction and distension of uterus
• distension of the vagina and perineum
• pressure on other organs and lumbosacral plexus

Sensory pathways

• Mild pain of early uterine contractions is conducted through T11–T12.
• When the pain becomes more intense, the pathway is T10–L1.
• The cervix is also supplied by T10–L1.
• Pain in the second stage is conducted via sacral segment S2–S5.

Analgesia in labour

Non-pharmacological methods

• position/postural changes
• warm or cold packs
• massage
• hydrotherapy
• transcutaneous electrical nerve stimulation (TENS), the electrodes being placed paravertebrally at T10–L1 and S2–S4 (uses the gate control theory of pain)
• hypnotherapy
• breathing techniques

Pharmacological methods

• Inhalational agents: nitrous oxide is simple and safe.
• Systemic opioid analgesia: pethidine has a more rapid onset (20–30 minutes, with peak effects at 1 hour) of action than morphine because of its higher lipid solubility. Neonatal depression can occur when administered 2–3 hours before delivery. Side effects include nausea, vomiting and reduced gastric motility.
• Regional anaesthesia: lumbar epidural is the most effective and reliable form of pain relief in labour. The local anaesthetic may be delivered by intermittent boluses or constant infusion.

Advantages of lumbar epidural

• The mother remains conscious, is able to maintain airways, and can participate in the birth.
• There is minimal or no fetal/neonatal depression with higher Apgar scores than those associated with narcotic analgesia.
• It may optimise uteroplacental blood flow and avoid increasing maternal/fetal acidosis and a further rise in maternal catecholamines.
• Better postpartum analgesia top-up pain relief is possible.
• It does not affect rates of caesarean section or obstetric intervention, though it may prolong the second stage.

Disadvantages of lumbar epidural

• It is not always successful in providing analgesia.
• There may be hypotension from reduced peripheral vascular resistance. This is a result of sympathetic blockade with decreased vasoconstriction and increased venous pooling. The blockade also produces a secondary tachycardia. Hypotension is managed with intravenous fluids and ephedrine 5–10 mg intravenously.

Complications of lumbar epidural

• Local anaesthesia toxicity. Central nervous system effects of circumoral numbness, restlessness, visual changes, confusion and convulsion, and arrhythmia and hypotension, are managed by ensuring adequate airway/ventilation, assessing cardiorespiratory status and treating convulsions.
• Massive subarachnoid injection of local anaesthetic. This is avoided by applying a small test dose. The complications, including hypotension, nausea, coma, fixed dilated pupils, phrenic nerve paralysis and ventilatory failure, are managed by providing ventilatory support, assessing cardiovascular status and giving intravenous fluids (maintain these until the anaesthetic wears off).
• Dural puncture. This occurs in about 1% of patients. The majority of these develop symptoms, especially positional headache. The most effective treatment is autologous blood patch, but there is a risk of infection.
• Anaphylactic reactions. Allergic and anaphylaxis reaction may occur as with any other pharmacological agents.

Paracervical block

• Relieves contraction pain in up to 80% of cases.

Spinal analgesia

• advantages: rapid onset, a dense block, and minimal risk of toxicity
• disadvantages: hypotension

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Chapter 41 Pain relief in labour

Michael Flynn

About two-thirds of women in labour consider the pain very severe and intolerable. There is a need for antenatal preparation, with balanced information and opportunity to discuss options of analgesia.

Pain in labour

Causes

• dilatation of the cervix
• contraction and distension of uterus
• distension of the vagina and perineum
• pressure on other organs and lumbosacral plexus

Sensory pathways

• Mild pain of early uterine contractions is conducted through T11–T12.
• When the pain becomes more intense, the pathway is T10–L1.
• The cervix is also supplied by T10–L1.
• Pain in the second stage is conducted via sacral segment S2–S5.

Analgesia in labour

Non-pharmacological methods

• position/postural changes
• warm or cold packs
• massage
• hydrotherapy
• transcutaneous electrical nerve stimulation (TENS), the electrodes being placed paravertebrally at T10–L1 and S2–S4 (uses the gate control theory of pain)
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