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Am Fam Physician. 2021;103(6):355-364

Patient information: See related handout on managing pain in labor, written by the authors of this article.

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial affiliations.

A patient's sense of empowerment and control is most predictive of maternal satisfaction with childbirth. Analgesia during labor greatly affects this experience. Individual patient priorities for labor pain management should be explored as part of routine prenatal care. Continuous labor support, water immersion, and upright positioning in the first stage of labor are associated with decreased use of pharmacologic analgesia. Despite the increased risk of adverse effects, self-administered inhaled nitrous oxide appears to be safe and effective for pain relief; however, its negative environmental impact as a greenhouse gas is a drawback. Evidence is lacking that any one opioid is superior in maximizing pain relief while minimizing adverse effects. Neuraxial anesthesia provides the most effective pharmacologic analgesia and is used in nearly three-fourths of labors in the United States. Neuraxial regional anesthesia is not associated with increased rates of cesarean delivery or assisted vaginal delivery, and it has only a small effect on the length of the second stage of labor. Epidural, spinal, combined spinal-epidural, and dural puncture epidural anesthesia are commonly used neuraxial techniques. Paracervical and pudendal blocks are safe and effective pain management options in specific circumstances. Both transversus abdominis plane block and subcutaneous wound infiltration with local anesthetic can decrease the use of postoperative analgesia. Patients with opioid use disorder require individualized pain management plans throughout perinatal care, and judicious opioid prescribing practices are encouraged for all patients.

Most patients will use some form of pharmacologic analgesia for pain management during labor. Although timeliness and adequacy of pain relief are important, they are not as predictive of maternal satisfaction with childbirth as the patient's sense of empowerment and control. Therefore, creating a supportive and nurturing environment should be a priority throughout the perinatal period.1

Health care professionals providing prenatal care should discuss options for labor pain management during routine prenatal visits and explore the patient's priorities for the labor experience. The effectiveness and associated risks of the various pain management approaches should be reviewed. Additionally, physicians should be familiar with and educate their patients on the available analgesia options; these options may vary among hospitals and birth centers. Anesthesia consultation should be considered in complicated cases (Table 1).2

ConsiderationExamples
Anticipated anesthetic complications or difficultyAnatomic anomaly of the head, neck, or spine
History of malignant hyperthermia
Known allergy or adverse response to anesthesia
Obesity (body mass index of at least 40 to 50 kg per m2, depending on facility)
Patient refusal of blood products
Cardiac conditionsCongenital cardiac anomalies (e.g., tetralogy of Fallot, transposition of the great vessels)
Congenital or acquired obstructive heart disease
Presence of a cardiac pacemaker or defibrillator
Pulmonary hypertension
Hematologic conditionsCoagulation disorders
Current anticoagulation
Thrombocytopenia
Hepatic conditionsCirrhosis or hepatitis with abnormal liver function or coagulopathy
Neuromuscular conditionsMultiple sclerosis
Muscular dystrophy
Renal conditionsChronic kidney disease
Spinal conditionsHistory of spinal surgery
Known arteriovenous malformation, Chiari malformation, ventriculoperitoneal shunt
Structural vertebral anomalies

Nonpharmacologic Approaches

Nonpharmacologic pain relief interventions are often used during labor, in place of or in addition to pharmacologic methods. Common nonpharmacologic interventions are summarized in Table 2.3

TypeDescriptionStage of laborEvidence
AcupunctureAcupuncture needles are applied to specific areas of the bodyFirstDecreases rates of assisted vaginal delivery and cesarean delivery; may decrease pain scores (limited studies)
Continuous labor supportTrained labor support person (often a doula) accompanies the patient throughout laborAllDecreases rates of assisted vaginal delivery and cesarean delivery; decreases use of pharmacologic analgesia; particularly helpful when outside support person, such as a friend or partner, is not present
HypnosisSelf-administered or non–self-administered hypnosisAntenatal and during all labor stagesDecreases use of pharmacologic analgesia
Maternal positioningUpright position, with the head above the hipsFirstDecreases use of epidural and cesarean delivery rate; can shorten first stage of labor by more than one hour
Sterile water injectionFour 1-mL injections of sterile water in specific areas on the sacrumFirstSmaller studies demonstrate reduced low back pain but no decrease in use of pharmacologic or regional anesthesia
Water immersionPatient is submerged in warm water, generally including the abdomenFirst stage is most common but also used in second stage through delivery (water birth)Decreases use of regional anesthesia and pain scores; increases maternal satisfaction with labor experience
OtherAromatherapy, audioanalgesia, heat/cold application, massage, TENS, biofeedback, rebozo (i.e., a traditional method using textile to manipulate pelvic movements)Various stagesInsufficient/limited evidence; pain scores generally not affected; may lead to some delay in use of pharmacologic analgesia

Continuous labor support, often from a doula, has been shown to increase rates of spontaneous vaginal delivery (relative risk [RR] = 1.08; 95% CI, 1.04 to 1.12), decrease the mother's negative feelings about the childbirth experience (RR = 0.69; 95% CI, 0.59 to 0.79), and decrease the use of pharmacologic analgesia (RR = 0.90; 95% CI, 0.84 to 0.96), especially when an outside support person, such as a friend or partner, is not present.4

Immersion in water during the first stage of labor can reduce the use of regional anesthesia (RR = 0.91; 95% CI, 0.83 to 0.99) with no difference in rates of spontaneous vaginal delivery, assisted vaginal delivery, postpartum hemorrhage, or third- or fourth-degree lacerations, and no difference in the duration of any stage of labor.5 Smaller studies suggest that injections of sterile water into the skin over the sacrum reduce labor-associated low back pain but do not meaningfully decrease the use of pharmacologic or regional anesthesia (RR = 0.86; 95% CI, 0.44 to 1.69).6

A Cochrane review demonstrated that patients in the first stage of labor who were in the upright position with the head above the hips, as opposed to recumbent positions, were less likely to use an epidural (RR = 0.81; 95% CI, 0.66 to 0.99) or have a cesarean delivery (RR = 0.71; 95% CI, 0.54 to 0.94).7 Another Cochrane review showed that upright positioning in the second stage of labor does not affect rates of cesarean delivery in patients who already have an epidural in place.8

Exercise ball maneuvers, lumbosacral massage, and warm showers during the first stage of labor may lower pain severity and delay or reduce the use of analgesic medications.9 Patients who use hypnosis during labor are less likely to use analgesic medications (RR = 0.73; 95% CI, 0.57 to 0.94), with no clear differences in spontaneous vaginal delivery rates, maternal satisfaction, or neonatal outcomes.10 Other interventions, such as aromatherapy and audioanalgesia, have not been shown to be beneficial.11

Systemic Pharmacologic Analgesia

Systemic medications commonly used for labor analgesia are listed in Table 3.1223

AdministrationCommon drugs and dosingOnset of action (minutes)Stage of laborChallenges/limitationsEvidence
Parenteral opioids1217
Patient-controlled intravenous, intravenous bolus, or intramuscularButorphanol, 1 to 2 mg IM or IV every 4 to 6 hours5 to 10 (IV), 30 to 60 (IM)FirstEvidence for pain control only within first two hours of administration; common maternal adverse effects: nausea, vomiting, dizziness, respiratory depression, oxygen desaturation, sedation; decreased fetal heart rate variability; crosses placenta, increased risk of neonatal respiratory depression when administered close to delivery; butorphanol and nalbuphine can precipitate withdrawal in patients taking chronic opioidsBetter pain control than parenteral nonopioid medications and nitrous oxide but inferior to neuraxial anesthesia
Fentanyl, 25 to 50 mcg IV every hour 2 to 4 (IV)
Morphine, 2 to 4 mg IM or IV every 2 to 4 hours (5 to 10 mg IM may be used in latent labor)3 (IV), 40 (IM)
Nalbuphine, 10 to 20 mg IM, IV, or SQ every 3 hours2 to 3 (IV), 15 (IM or SQ)
Remifentanil (Ultiva), typically used as a background infusion of 0.05 to 0.1 mcg per kg plus boluses of 0.2 to 0.5 mcg per kg with lockout intervals of 2 to 3 minutes1 to 2
Parenteral nonopioids (analgesics, antihistamines, sedatives)16,1821
Oral, intravenous, or intramuscularAcetaminophen, 1,000 mg orally or IV every 6 hours60 (IV), 10 (oral) FirstAcetaminophen: may not control pain adequatelyImproves pain scores but less than parenteral opioids
Diphenhydramine (Benadryl), 25 to 50 mg orally, IV, or IM every 4 to 6 hours1 (IV), 5 (IM)Diphenhydramine and promethazine: maternal somnolence and dissociation from birth
Promethazine, 50 mg orally or IM or 25 mg IV every 4 to 6 hours20 (oral and IM), 2 to 5 (IV)
Inhaled medication (nitrous oxide, fluranes)22,23
Self-administered via handheld mask50:50 mix of nitrous oxide and oxygen gas< 1First and secondMaternal nausea, vomiting, dizziness, drowsiness; effect ends quickly once mask is removed; potent greenhouse gasImproves pain scores; rapid clearance once mask is removed

NITROUS OXIDE

Inhaled analgesia may be beneficial for patients in labor who desire some form of noninvasive pharmacologic pain relief.22 Self-administered inhaled nitrous oxide may provide patients with a greater sense of control in labor and, with an onset of action within one minute, may be safe and effective for pain relief. A Cochrane review demonstrated that placebo or no treatment provides inferior pain relief compared with nitrous oxide in the first stage of labor (RR = 0.06; 95% CI, 0.01 to 0.34).22 However, nitrous oxide increases the risk of maternal adverse effects, such as nausea (RR = 43.10; 95% CI, 2.63 to 706.74), vomiting (RR = 9.05; 95% CI, 7.09 to 1,833.69), and drowsiness (RR = 77.59; 95% CI, 4.80 to 1,254.96).22 Because anesthetic gases contribute to greenhouse gas emissions, the environmental impact of routine use of nitrous oxide should also be considered.23

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