Obstetric Pain Management

Labor can be extremely painful, and adequate pain management during labor and delivery is an important part of obstetric care. Appropriate therapy should be administered based on patient preference and medical need. Both pharmacological and non-pharmacological pain control options are available. Maternal request alone is sufficient indication for pharmacologic pain management. Options include systemic analgesics, including inhaled nitrous oxide and opioids, as well as local and regional techniques, including pudendal nerve blocks, epidural, and spinal anesthesia. In truly emergent situations requiring urgent cesarean delivery, general anesthesia can also be used.

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Overview

Definition

Obstetric pain management refers to the pharmacological and non-pharmacological options available to help manage discomfort during labor and delivery. Such options include spontaneous vaginal deliveries and cesarean deliveries.

Maternal perceptions of labor pain

  • Labor pain is influenced by a woman’s emotional, motivational, cognitive, social, and cultural circumstances.
  • Perception can vary significantly between women.
  • Pain may be affected by:
    • Fetal position
    • Shape and size of the maternal pelvis
    • Maternal parity (i.e., nulliparous vs. multiparous women)
    • Status of the fetal membranes (i.e., ruptured vs. intact)
    • Medical comorbidities (e.g., fibromyalgia)
    • Obstetric complications (e.g., intraamniotic infection)

Non-pharmacological pain management techniques

  • Ambulation
  • Position changes
  • Massage
  • Warm water (e.g., shower, bath)
  • Meditation/self-hypnosis

Indications for pharmacological pain management

According to the American College of Obstetrics and Gynecology (ACOG), “There is no other circumstance in which it is considered acceptable for an individual to experience untreated severe pain that is amenable to safe intervention while the individual is under a physician’s care.”

  • For patients in labor, maternal request alone is sufficient indication for pain control.
  • Appropriate pain management options should be offered to all patients.
  • Therapy should be administered based on patient preference:
    • A sense of personal control over decision-making is more important than absolute levels of pain. 
    • Postpartum depression (PPD) and PTSD are associated with uncontrolled pain.
  • Absent medical contraindications, patients may choose:
    • When to start labor analgesia
    • What type of analgesia they prefer
    • Whether or not they want labor analgesia at all 

Options for pharmacologic pain management

  • Systemic analgesics
  • Local and regional analgesics
  • General anesthesia

Physiology

Pain in the 1st stage of labor

The 1st stage of labor begins with the onset of regular uterine contractions causing cervical change and ends when the patient’s cervix is fully dilated at 10 cm.

Pain in the 1st stage of labor is:

  • Visceral cramping pain
  • Originates from:
    • Ischemia of the uterus during contractions
    • Distension of the cervix
    • Referred pain to the abdominal wall, lumbosacral region, and upper legs
  • Perceived by nerves T10–L1

Pain in the 2nd stage of labor

The 2nd stage of labor begins when the cervix is fully dilated at 10 cm and ends with expulsion of the fetus.

  • Pain typically described as more severe
  • Often perceived as intense rectal pressure
  • Due to a combination of:
    • Visceral pain from the uterus and cervix
    • Somatic pain from distension of the vagina and perineum
  • Somatic pain is transmitted through the pudendal nerve (S2–S4).

Systemic Analgesics

Systemic analgesics can be used during labor but are not adequate for cesarean deliveries. They are commonly chosen by women for management of earlier labor, prior to getting an epidural.

Inhaled analgesia: nitrous oxide (“laughing gas”)

  • Inhaled intermittently, during contractions only
  • Self-administered by patient
  • Pain relief: minimal and short lasting
  • Side effects: lightheadedness, dizziness, and nausea
  • Provides some pain relief early in labor
  • For patients who prefer to avoid other options 

IV analgesia: opioids

  • May be given as:
    • Intermittent IV bolus of standard-dose opioids
    • Patient-controlled analgesia:
      • May or may not include a low-dose continuous infusion (basal rate)
      • Patients can self-administer small boluses.
  • Intermittent IV bolus options (usually administered every 2–4 hours):
    • Nalbuphine 
    • Meperidine
  • Patient-controlled analgesia options:
    • Remifentanil
    • Fentanyl
  • Pain relief: 
    • Minimal to moderate 
    • Short lasting 
    • Provides more relief than nitrous oxide but significantly less than an epidural
  • Side effects: nausea, vomiting, and drowsiness
  • Can affect the fetus because opioids cross placenta, leading to:
    • Decrease in fetal heart rate (FHR) variability
    • Fetal respiratory depression if drugs remain in the fetal system after delivery → avoid giving opioids within 4 hours of delivery

Local and Regional Analgesic Techniques

Pudendal nerve block

  • Injection of opioids into the pudendal nerve (S2–S4) 
  • Pain relief: 
    • Excellent along the nerve distribution
    • Effect covers the lower vagina, labia, and perineum only.
  • Used for: 
    • Operative vaginal deliveries and laceration repairs in patients without epidurals
    • Additional pain control when epidural anesthesia fails to adequately anesthetize the sacral nerves
  • Does not provide analgesia for uterine pain and is not helpful for:
    • Contraction pain during labor
    • Cesarean deliveries
  • Complications: hemorrhage due to inadvertent laceration of the pudendal artery
Site of injection for a pudendal nerve block

Site of injection for a pudendal nerve block

Image by Lecturio. License: CC BY-NC-SA 4.0

Epidural anesthesia

  • Slow-flow continuous administration of opioid into the epidural space via a catheter
  • Pain relief:
    • Continuous pain relief while running
    • Excellent pain relief at T8 and below
    • May have some “hot spots” (areas of poor pain relief)
  • Used for: 
    • Labor pain management through vaginal delivery
    • Cesarean deliveries: 
      • Typically used only after failed trials of labor when the epidural is already in place (e.g., arrested labor)
      • Spinal anesthesia is superior to epidurals for cesarean delivery due to a lack of “hot spots.”
  • Maternal side effects: hypotension (may cause uteroplacental insufficiency until corrected)
  • Contraindications: 
    • Certain coagulopathies
    • Increased intracranial pressure
    • Skin infections in the lower back
Location of epidural catheter placement

Location of epidural catheter placement

Image by Lecturio. License: CC BY-NC-SA 4.0

Spinal anesthesia

  • Single injection of opioid into the subarachnoid space
  • Pain relief: 
    • Lasts 2–4 hours 
    • Excellent pain relief at T10 and below
  • Used for: cesarean deliveries
  • Maternal side effects of spinal anesthesia:
    • Hypotension (may cause uteroplacental insufficiency until corrected)
    • Bradycardia
Spinal anesthesia location of opioid injection

Location of opioid injection during spinal anesthesia

Image by Lecturio. License: CC BY-NC-SA 4.0

Regional anesthesia

Table: Regional anesthesia
Epidural anesthesiaSpinal anesthesia
Site of injectionEpidural spaceSubarachnoid space
Level of injectionT8T10
Duration of pain reliefContinuous while catheter remains in place2–4 hours
Side effectsHypotensionHypotension and bradycardia

General Anesthesia

  • Reserved for emergency C-sections: Spinal anesthesia should always be attempted first if time allows and unless there are specific contraindications.
  • Increases risk for:
    • Maternal aspiration → aspiration pneumonitis
    • Postpartum hemorrhage (general anesthesia causes uterine atony)
    • Fetal respiratory depression at birth
  • Fetal care:
    • Pediatric care providers should be present at delivery to provide respiratory support, as the infant will also be under the effects of general anesthesia.
    • Infants should be delivered as quickly as possible after induction of anesthesia to minimize fetal effects.

References

  1. Lowe, NK. (2002). The nature of labor pain. Am J Obstet Gynecol. 186(5 Suppl Nature), S16–24. https://pubmed.ncbi.nlm.nih.gov/12011870/ 
  2. Melzack, R, Taenzer, P, Feldman, P, & Kinch, RA. (1981). Labour is still painful after prepared childbirth training. Can Med Assoc J. 125(4), 357–63. https://pubmed.ncbi.nlm.nih.gov/7272887/ 
  3. Hodnett, ED. (2002). Pain and women’s satisfaction with the experience of childbirth: A systematic review. Am J Obstet Gynecol. 186(5 Suppl Nature), S160–72. https://pubmed.ncbi.nlm.nih.gov/12011880/ 
  4. Brownridge, P. (1995). The nature and consequences of childbirth pain. Eur J Obstet Gynecol Reprod Biol. 59 Suppl, S9–15. https://pubmed.ncbi.nlm.nih.gov/7556828/ 
  5. Goetzl, LM, ACOG Committee on Practice Bulletins-Obstetrics. (2002). ACOG Practice Bulletin. Clinical Management Guidelines for Obstetrician-Gynecologists Number 36, July 2002. Obstetric analgesia and anesthesia. Obstet Gynecol. 100(1), 177–91. https://pubmed.ncbi.nlm.nih.gov/12100826/ 
  6. Committee on Obstetrics. (2019). American College of Obstetrics and Gynecology Practice Bulletin No. 209: Obstetric Analgesia and Anesthesia. Retrieved May 27, 2021, from https://www.acog.org/clinical/clinical-guidance/practice-bulletin/articles/2019/03/obstetric-analgesia-and-anesthesia 

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