Skip to textbook content
Doctor’s PassportTextbook
QuestionsFlashcardsBriefsDashboardAccount
TopicsAll topics

Loading topic navigation…

Textbook navigation
TopicsAll topics

Loading topic navigation…
← Obstetrics and gynaecology indexChapter sections
Purpose and principlesIndications, selection and cautionsAssessment before treatmentTreatment approachRegimens, contraindications and interactionsComplications, monitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
Full textbook10 sectionsOpen only what you need
Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Pain relief in labour

Obstetrics and gynaecology · UK scope · Sources checked 7 Sept 2026 · Clinical review pending

RapidFull
!
Respiratory depression or an unexpectedly high block

Marked drowsiness, slow or absent breathing, falling oxygen saturation, rapidly ascending numbness, arm weakness or cardiovascular collapse after analgesia requires immediate assessment. Do not attribute reduced responsiveness to exhaustion alone.

Action: Stop the implicated opioid or neuraxial administration, call the anaesthetist and emergency team, and assess airway, breathing and circulation. Provide oxygen and ventilatory support as required, position to reduce aortocaval compression and begin the appropriate anaesthetic emergency pathway while monitoring the fetus.

Purpose and principles

Help patients choose effective labour analgesia, explain important trade-offs, and identify sedation or neuraxial complications that require immediate anaesthetic assessment.

Labour pain combines visceral sensation from uterine contractions and cervical change with later pressure and somatic pain from the pelvic floor and perineum. Its experience is influenced by fatigue, fetal position, previous experiences, fear, support and the environment. The goal is relief that the patient considers useful while preserving safety and informed choice. A method that worked well earlier may no longer meet the patient's needs, and changing the plan does not represent failure.

Discuss available options antenatally where possible, then revisit them during labour. Explain likely benefit, onset, duration, side effects and any effect on mobility, monitoring or place of birth. Some methods, such as epidural or remifentanil PCA, require an obstetric setting and trained staff. The ability to request an epidural should not depend on reaching an arbitrary cervical dilatation. At the same time, an imminent birth or an anaesthetic contraindication can alter which option is practical.

Key points

Indications, selection and cautions

Assessment of pain and preference

Ask what the pain feels like, where it is located, how the patient is coping and what degree of relief they want. Review previous experience and concerns about needles, sedation or loss of control. Continuous focal pain or pain outside contractions may need assessment beyond an analgesic prescription.

Safety before systemic opioids

Check previous opioid doses, other sedating medicines, respiratory disease, renal or hepatic impairment and likely proximity to birth. Sedation can outlast useful analgesia. Discuss nausea, vomiting, drowsiness and possible effects on neonatal breathing and early feeding.

Assessment before regional analgesia

The anaesthetist reviews medical history, allergies, anticoagulants, bleeding risk, infection, relevant examination and available blood results. Thrombocytopenia and anticoagulant timing require individual assessment rather than one universal rule. Establish intravenous access and explain the procedure and potential complications.

An incomplete or changing block

Unilateral pain, missed segments or renewed severe pain may indicate an ineffective catheter, advancing labour or another clinical problem. Reassess the block and symptoms rather than repeatedly administering medication without checking catheter function, maternal observations and the fetal heart.

Red flags requiring action

  • Inability to remain awake, respiratory depression or desaturation during opioid analgesia requires immediate intervention.
  • Breathlessness, difficulty speaking, arm weakness or rapidly increasing numbness after an epidural dose raises concern for a high neuraxial block.

Assessment before treatment

  1. 01
    Respiratory and sedation assessmentFirst step
    Why
    Detect systemic opioid effects before ventilation becomes unsafe.
    Interpretation and limitations
    Observe breathing and responsiveness, using pulse oximetry where indicated. With remifentanil PCA, continuous respiratory observation and pulse oximetry are required. Supplemental oxygen can improve saturation without correcting inadequate ventilation, so it does not replace direct observation.
  2. 02
    Blood pressure and fetal monitoring
    Why
    Identify haemodynamic effects when regional analgesia is established.
    Interpretation and limitations
    Measure maternal blood pressure every five minutes for fifteen minutes during establishment and after further boluses of 10 mL or more of low-dose solution. Use CTG during establishment and for at least thirty minutes after such boluses, then continue according to the complete risk assessment.
  3. 03
    Blood count and clotting assessment when indicated
    Why
    Clarify bleeding risk before neuraxial instrumentation or catheter removal.
    Interpretation and limitations
    Testing depends on the history and conditions such as pre-eclampsia, haemorrhage or anticoagulant exposure. A recent result must be interpreted against the direction of change and clinical condition; a normal routine clotting screen does not negate relevant anticoagulant timing.
  4. 04
    Sensory and motor block examination
    Why

Treatment approach

01Initial and evolving painOffer a range of practical choicesFirst stepThe patient requests pain relief or the current approach is no longer sufficient.+
  1. 1Explain the options available in the current setting and ask which benefits and drawbacks matter most to the patient.
  2. 2Offer supportive care, comfortable positions, breathing techniques, massage and access to water where suitable, without making these a prerequisite for stronger analgesia.
  3. 3Consider inhaled nitrous oxide with oxygen, sterile water injections for back pain, or a systemic opioid with an antiemetic as appropriate.
  4. 4Reassess relief, side effects and the stage of labour, and arrange transfer or anaesthetic review if the patient requests a method unavailable locally.
02Regional analgesiaEstablish and maintain effective neuraxial reliefAn epidural or combined spinal–epidural is requested and anaesthetic assessment supports its use.

Regimens, contraindications and interactions

Provides rapidly adjustable partial analgesia during contractions and procedures.

Nitrous oxide with oxygen, Entonox

Use the premixed 50% nitrous oxide and 50% oxygen gas through a patient-held demand system. Begin inhalation as a contraction starts and stop according to comfort, dizziness or nausea.

The patient must remain able to use the device safely. Review impaired consciousness and conditions involving trapped gas spaces or relevant vitamin B12 risk; increasing sedation from other medicines changes the assessment.

Offers systemic analgesia when the patient chooses an injectable opioid.

Pethidine injection

The cited UK SmPC obstetric regimen is 50–100 mg intramuscularly or subcutaneously, with a further dose 1–3 hours later if needed, to a maximum of 400 mg in 24 hours. The maternity prescription should select dose and timing after assessment.

Give an antiemetic and reassess sedation and breathing before another dose. The product contraindicates severe respiratory depression, severe obstructive airways disease or acute asthma, severe renal or hepatic impairment, and MAOIs taken within the previous two weeks, including moclobemide, selegiline and rasagiline. Review other sedatives and proximity to birth; avoid a bath or pool for two hours after administration and while drowsy.

Provides short-acting systemic analgesia for patients wanting ongoing labour pain relief.

Remifentanil patient-controlled analgesia

NICE describes 40 micrograms intravenously per patient-triggered bolus with a two-minute lockout interval for labour analgesia. This obstetric use is outside the usual anaesthesia licence and requires the unit's specific PCA preparation and safety pathway.

Complications, monitoring and follow-up

  • Reassess pain relief from the patient's perspective, recording both useful benefit and adverse effects rather than pain scores alone.
  • Maintain stage-appropriate fetal surveillance and increase monitoring when analgesia-related or other clinical risks emerge.
  • During regional analgesia, assess sensory block hourly and, if the patient is not mobilising, assess motor block hourly using a straight-leg raise. Obtain anaesthetic review if satisfactory pain relief has not occurred within 30 minutes after a dose.
  • Review bladder function and fluid balance during regional analgesia, avoiding unnecessary fluid loading and supporting regular emptying.
  • After birth, reassess residual block and mobility before unassisted walking, and provide clear advice about headache, back pain, weakness or bladder symptoms.
  • Document any difficult procedure, accidental dural puncture, inadequate block or respiratory event so that postnatal teams can arrange follow-up.

Special situations

Back pain has an additional option

For labour-related back pain, NICE allows sterile water injections at four points around the rhombus of Michaelis: 0.1 mL intracutaneously or 0.5 mL subcutaneously per point. Explain the initial stinging sensation and variable duration of benefit.

An epidural does not mandate caesarean birth

Discuss the actual trade-offs, including monitoring, possible incomplete effect and second-stage implications. Do not tell patients that epidural analgesia inevitably causes caesarean birth or persistent back pain.

Water needs a current safety assessment

Water can support comfort, but drowsiness after opioids changes safety. The decision to enter or remain in water must consider maternal alertness, observations, fetal risk and the ability to leave promptly if care needs change.

Unexpected pain can be diagnostic

A previously comfortable patient with sudden focal or constant pain needs reassessment of the obstetric situation as well as the block. Additional analgesia should not conceal investigation of bleeding, uterine tenderness or maternal instability.

Common pitfalls

  1. 01

    Delaying requested analgesia solely because cervical dilatation is considered too early.

  2. 02

    Describing remifentanil as safe without continuous respiratory supervision because it wears off quickly.

  3. 03

    Allowing a companion to press the PCA button for a sleepy patient.

  4. 04

    Giving repeated epidural boluses without reviewing an ineffective or unexpectedly extensive block.

  5. 05

    Assuming normal oxygen saturation excludes hypoventilation when supplemental oxygen is being given.

Practice

Two practice questions

Your practice draft is saved in this browser.

Question 1 of 2
0 correct
Obstetrics and gynaecologyOriginal SBA

Select the NICE remifentanil regimen

A woman has chosen remifentanil PCA in an obstetric unit with continuous trained one-to-one care, respiratory monitoring and immediate anaesthetic support. Which bolus and lockout combination is the regimen described by NICE for labour analgesia?

Choose one answer, then submit
← Rapid synopsisBack to overviewAll Obstetrics and gynaecology topics →
Sources and review status4 sources · checked 7 Sept 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 7 Sept 2026; clinical approval remains outstanding.

  • NICE NG235 pain relief and regional analgesia
  • Pethidine injection product characteristics
  • Remifentanil product characteristics
  • NHS pain relief in labour

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
The patient's request, clinical situation and preferences guide analgesia; there is no requirement to endure a fixed level of pain first.
  • Support, movement, breathing techniques, massage and water can help, and may be combined with pharmacological methods.
  • Inhaled nitrous oxide with oxygen is rapidly adjustable but often provides partial relief and may cause nausea or light-headedness.
  • Intramuscular opioids provide limited labour analgesia and can cause maternal sedation and neonatal respiratory depression.
  • Epidural analgesia is more effective than systemic opioids and requires anaesthetic assessment, appropriate monitoring and a plan for inadequate effect.
  • Remifentanil PCA is restricted to obstetric units with continuous trained one-to-one care, respiratory monitoring and immediately available anaesthetic support.
  • An analgesic plan should be reviewed when labour progresses, the patient changes preference or a new maternal or fetal concern appears.
    • Severe hypotension or a new fetal heart abnormality after regional analgesia needs prompt assessment and treatment.
  • New severe back pain with neurological deficit or bladder dysfunction after neuraxial treatment requires urgent specialist investigation.
  • Fever with spinal pain, or a severe persistent postpartum headache, warrants assessment rather than routine reassurance.
    • Assess analgesic distribution and detect excessive neuraxial spread.
    Interpretation and limitations
    Record the extent of sensory change and motor function during epidural care, with review after new symptoms or additional doses. Mobility requires an assessment of strength, sensation and stability with appropriate assistance, rather than the assumption that a low-dose solution always permits walking.
    +
    1. 1Discuss benefits, alternatives, procedure-specific risks and the possibility of incomplete relief or catheter replacement, then obtain consent.
    2. 2Establish intravenous access and appropriate maternal and fetal monitoring, and administer the initial neuraxial dose cautiously as a test of catheter location and response.
    3. 3Maintain relief using a low-concentration local anaesthetic with opioid through patient-controlled epidural dosing, programmed intermittent bolus or trained clinician boluses.
    4. 4EscalationReview inadequate relief promptly and escalate hypotension, excessive block or new neurological symptoms rather than treating them as expected discomfort.
    5. 5Plan bladder care, assisted mobility and second-stage management, and document postnatal review if there was a complication or persistent symptom.
    03Remifentanil optionLink analgesia to continuous respiratory careThe patient chooses intravenous remifentanil PCA after discussion of its risks and benefits.+
    1. 1Use an obstetric unit with a midwife trained in remifentanil care continuously present and immediate anaesthetic support available.
    2. 2Check the prescribed bolus, lockout interval, dedicated administration arrangements and any recent sedating medication before starting.
    3. 3Ensure only the patient operates the button, with continuous observation of breathing and pulse oximetry; provide CTG when other risk factors indicate it.
    4. 4Stop administration and call for help with excessive sedation, abnormal breathing or desaturation, providing airway and ventilatory support when needed.
    5. 5PreferredContinue reviewing whether the analgesic benefit is sufficient or whether another option, including regional analgesia, is now preferred.

    Continuous trained one-to-one presence, direct respiratory observation, pulse oximetry, immediate oxygen and anaesthetic support are essential. A short half-life does not prevent apnoea, and a companion must never trigger doses.

    Produces effective regional analgesia with lower local anaesthetic concentrations.

    Low-dose epidural local anaesthetic and fentanyl

    NICE recommends maintenance solutions of bupivacaine 0.0625–0.1% or equivalent with fentanyl 2 micrograms/mL. The anaesthetist selects bolus volumes, lockout and delivery mode according to the catheter, block and clinical response.

    Concentration alone is not a complete prescription. Initial and additional doses need appropriate haemodynamic and block assessment, with immediate readiness to manage intravascular injection, high block or cardiovascular effects.