Module VII — Pain Control During Labor & Delivery

1. Nature of Labor Pain

• Labor pain is highly individual — shaped by emotional, motivational, cognitive, social, and cultural factors.
• Often the most severe pain a woman experiences in her lifetime; many nulliparas rate it as very severe or intolerable.
• Pain varies by individual and by pregnancy (e.g., occiput posterior position → more severe pain).
• Pain originates from different sites as labor progresses.

2. Anatomy & Physiology of Labor Pain

First Stage of Labor

• Pain is visceral/cramp-like, arising from the uterus and cervix.
• Caused by: distention of uterine/cervical mechanoreceptors + ischemia of uterine/cervical tissues.
• Pain signal travels via T10, T11, T12, L1 white rami communicantes into the spinal cord.
• Visceral fibers pass through the Frankenhauser ganglion → pelvic plexus → lumbar & lower thoracic sympathetic chains.
• Early labor pain transmitted predominantly through T11 and T12.
• Motor pathways to the uterus leave the cord at T7–T8 — sensory block without motor block is theoretically possible.
• Pain can be referred to: abdominal wall, lumbosacral region, iliac crests, gluteal areas, thighs.

Transition (Late First Stage → Second Stage: 7–10 cm dilation)

• Shift to greater nociceptive input; somatic pain from vaginal distention begins.

Second Stage of Labor

• Somatic pain from distention of vagina, perineum, pelvic floor + stretching of pelvic ligaments.
• Transmitted via S2, S3, S4 (pudendal nerve).
• More severe than first stage; combination of visceral (uterine contractions, cervical stretching) + somatic.
• Woman also experiences rectal pressure and urge to bear down.
• Pudendal nerve passes beneath the posterior surface of the sacrospinous ligament at the ischial spine.

3. Physiological & Psychological Effects of Unrelieved Pain

Epidural analgesia reverses adverse ventilatory effects and decreases maternal epinephrine, cortisol, and beta-endorphin levels.

4. Two General Approaches to Pain Management

Suffering = perceived threat to body/psyche + helplessness + distress + fear of death. One may suffer without pain, or have pain without suffering.

5. Nonpharmacologic Methods

Recommendation (Grade 1B): Offer all women nonpharmacological methods to help cope with labor.

5a. Environment

• Home-like settings → ↑ likelihood of not using analgesia (RR 1.19), ↑ satisfaction (RR 1.14), ↑ desire for same setting next time (RR 1.81).

5b. Continuous Emotional Support

• Kennell et al. (1991): Continuous support → cesarean rate 8% vs 13%, epidural use 8% vs 23% (p<0.05).
• Fear and the unknown potentiate pain.

5c. Water Immersion (Hydrotherapy)

• Water at or slightly above body temperature; covers abdomen; typically used during first stage.
• 4 of 8 RCTs: significant pain reduction; none showed reduced epidural use.
• Safe — no increased maternal or neonatal infection risk, even with ruptured membranes.
• Limitation: inadequate data for clear recommendations on timing/duration.

5d. Intradermal Water Blocks

• 4 intradermal injections of 0.05–0.1 mL sterile water (1 mL syringe, 25-gauge needle) → 4 blebs:
  • Over each posterior superior iliac spine (PSIS)
  • 2 more sites: 3 cm below and 1 cm medial to PSIS
• Mechanism: "gate control" + local endorphin release. Physiological saline does not work — must be sterile water.
• Pain relief lasts 45–120 minutes.
• Injections are transiently painful; administer during a contraction or simultaneously by 2 providers.
• All 5 RCTs: significantly reduced severe low back pain during labor.
• No fetal/maternal side effects.

5e. Movement & Positioning

• First stage: Upright positions (sitting, standing, walking) > supine or lying on side — less painful.
• Second stage: Kneeling > sitting; supine associated with most pain.
• 16 controlled trials: supine was never rated more comfortable than other positions.

5f. Touch & Massage

• No harmful effects; reduces pain and enhances well-being.

5g. Acupuncture / Acupressure

• Acupuncture: trend toward less pharmacological analgesia (RR 0.70, 95% CI 0.49–1.00); no significant reduction in pain intensity scores.
• Acupressure (Shiatsu): 2 RCTs showed decreased pain vs. control.
• No known risks (trained practitioner, disposable needles).
• Note: Powerful placebo effect — sham acupuncture controls are important.

5h. Hypnosis

• Almost always self-hypnosis taught before labor.
• Techniques: "glove anesthesia," "time distortion," "imaginative transformation."
• Systematic review: significant reduction in pharmacological analgesia (RR 0.53, 95% CI 0.36–0.79); one trial showed decreased epidural use.
• Contraindicated in history of psychosis.

5i. Relaxation & Breathing Techniques

• 49% of US women (2005 survey) used breathing techniques; 77% found them "very" or "somewhat" helpful.
• British survey: 88% found relaxation techniques "good" or "very good."
• Contribute more to coping ability than actual pain reduction.
• No known drawbacks; should be included in childbirth education classes.

5j. Aromatherapy

• Increasingly used but no RCT data.
• Prospective study (n=8058): ~50% found helpful; 1% reported nausea/headache.
• Caution: essential oils are potent — use lowest dose.

5k. Audioanalgesia (Music)

• Cochrane review: music reduced pain intensity and opioid requirements — effect is small.
• No known adverse effects; use should be encouraged.

6. Pharmacologic Methods

6a. Systemic Opioids

• Work in the maternal brain → relief by inducing somnolence rather than true analgesia.
• A portion crosses the placenta and affects the fetus.

• Serotonergic crisis, seizures
• Normeperidine toxicity
• Multiple drug interactions (e.g., MAO inhibitors)

• Satisfaction with opioid pain relief: only 29% vs 17% placebo (marginally better).
• No opioid significantly more effective than meperidine.
• Epidural analgesia provides better pain relief than parenteral opioids.
• Opioids → shorter labor, less oxytocin augmentation, fewer instrumental deliveries vs. epidural.

Key rules:

• Administer with an antiemetic.
• Woman should not enter water within 2 hours of opioid or if drowsy.
• Consider alternatives if fetus is at high risk or shows non-reassuring FHR.

6b. Nitrous Oxide (Entonox)

• 50:50 mixture of O₂ and N₂O — self-administered via hand-held face mask.
• Safety: parturient drops mask if too drowsy → automatic cessation.
• Disadvantage: difficult to scavenge → environmental pollution.
• Analgesic effect: better than opioids, less than epidural.
• Entonox should be available in all birth settings.
• May cause nausea and light-headedness.

7. Regional Analgesia (Epidural / Spinal)

Most reliable means of pain relief during labor and delivery.

7a. Technique

• Epidural: Local anesthetic (0.02–0.125% bupivacaine or 0.04–0.2% ropivacaine) via continuous infusion; combined with neuraxial opioids for lower concentrations to be effective.
• Neuraxial opioids alone provide excellent analgesia for early first stage.
• An in-situ epidural catheter can be used for instrumental or cesarean delivery.

7b. Access

• Only available in obstetric units.
• Women desiring regional analgesia should not be denied it, including in the latent first stage.

7c. Monitoring After Epidural

• Blood pressure every 5 minutes for 15 minutes after establishment or further boluses (≥10 mL).
• If not pain-free 30 minutes after administration → recall anesthetist.
• Hourly sensory block level assessment.
• Continuous EFM for at least 30 minutes during establishment and after each bolus ≥10 mL.

7d. Benefits

• More effective than opioids.
• Blocks maternal stress response; reverses physiological consequences of pain.
• Not associated with long-term backache.
• Not associated with longer first stage or increased cesarean rate.
• Neonates less likely to need naloxone vs. opioid analgesia.

7e. Risks / Considerations

• Associated with longer second stage and increased instrumental vaginal delivery rate.
• Mechanisms of increased instrumental delivery:
  • ↓ serum oxytocin → weakened uterine activity
  • IV fluid infusion before epidural → ↓ oxytocin secretion
  • Impaired maternal expulsive efforts → fetal malposition during descent
• Not associated with increased cesarean section risk.
• Ultra-low concentrations may be inadequate in second stage (requirements increase as labor progresses).
• Opioids in epidural solutions cross the placenta; >100 mcg total → short-term neonatal respiratory depression.

7f. Management with Epidural in Place

• Encourage mobility and upright positions throughout labor.
• Continue epidural until after third stage and perineal repair.
• On reaching full dilation: if no urge to push and head not visible → delay pushing for at least 1 hour (longer if desired).
• Delivery should occur within 4 hours of confirmed full dilation.
• Oxytocin should not be used routinely in second stage with epidural.
• Delaying pushing until head is visible or 1 hour post-dilation → reduces instrumental delivery rate.

8. Anesthesia Service Standards (ACOG/ASA Goals)

1. Licensed credentialed practitioner available for appropriate anesthetic at all times.
2. Anesthesia personnel to start cesarean within 30 minutes of decision.
3. Emergency cesarean capability during active labor for VBAC women.
4. Qualified anesthesiologist responsible for all anesthetics.
5. Physician with obstetric privileges available during anesthesia.
6. Equipment/facilities equal to surgical suite standards.
7. Personnel for neonatal resuscitation other than the surgical team.

Reimbursement for regional analgesia given solely for pain relief should not be denied (ACOG/ASA Joint Statement, 2004).

9. Endogenous Opioid System (Stress Analgesia)

• Stress releases endogenous opioids → inhibit pain impulse transmission in brain and spinal cord.
• Endogenous opioids act on opioid receptors → inhibit release of Substance P (pain hormone) → universal analgesic effect.
• Higher opioid concentration → higher pain threshold.
• Stress analgesia in labor: the same pain stimulus that would cause shock in a non-pregnant woman is tolerated in a laboring woman due to this mechanism.

10. Key Take-Home Points

• Pain relief is a right — a woman's request is sufficient medical indication.
• Nonpharmacological methods are low-risk, inexpensive, and improve coping, satisfaction, and sense of control — offer them to all women.
• Measuring coping ability and timing of pharmacological analgesia are more meaningful outcomes than pain scores alone.
• Nonpharmacological methods (TENS, water immersion, intradermal water blocks) can delay pharmacological analgesia, reducing cumulative dose and associated risks.
• Epidural analgesia is the most effective but comes with trade-offs (instrumental delivery, monitoring burden).
• Healthcare professionals should examine their own values and ensure care supports the woman's choice.