Table 2Inclusion and exclusion criteria

Study populationPregnant women in first and second stages of labor (up to birth), other attendees and health care providers, and the fetus/neonate
InterventionNitrous oxide inhalation
  • No analgesic/anesthetic intervention, analgesia/anesthesia, other inhalational agents, and pharmacologic and nonpharmacologic pain management methods
    • Pharmacologic pain management methods include, but are not limited to, epidural analgesia, paracervical block, pudendal block, and parenteral opioids
    • Nonpharmacologic pain management methods include, but are not limited to, acupuncture, aromatherapy, continuous labor support, heat and cold, hydrotherapy, hypnosis, movement and positioning, music and audioanalgesia, patterned breathing and relaxation, sterile water injections, touch and massage, and transcutaneous electrical nerve stimulation (TENS)
  • Primary outcomes:
    • Pain reduction
    • Satisfaction with pain management
    • Satisfaction with birth experience
    • Long-term maternal, child, and occupational health outcomes
  • Other outcomes:
    • Labor and intermediate outcomes



      Labor progress

      Satisfaction with pain management.

      Satisfaction with birth experience

      Availability and timeliness

      Cointerventions associated with the use of nitrous oxide or other pain management methods

    • Birth and long-term outcomes

      Maternal outcomes, including but not limited to route of birth and postpartum course

      Child outcomes, including but not limited to Apgar scores, fetal cord blood gases, and neurobehavioral outcomes

      Health care provider outcomes (occupational health) from exposure

      Maternal satisfaction with pain management

      Maternal satisfaction with birth experience

    • Adverse effects, including but not limited to:

      Maternal adverse effects, such as nausea and vomiting, dreams, dizziness, and unconsciousness

      Fetal/neonatal adverse effects, such as drug dependency

      Childhood adverse effects, such as drug dependency and developmental complications.

      Individuals present for labor adverse effects.

      Health care provider adverse effects (occupational health)

  • Intermediate outcomes will include associated labor outcomes
  • Long-term outcomes will include associated birth outcomes
  • There will be no restriction on duration of follow-up
  • All birth settings will be considered, including hospital, birth center, and home
Publication dateNo limit
Publication languagesEnglish only
Admissible evidence (study design and other criteria)Admissible designs
  • Study size ≥20 pregnant women using nitrous oxide during labor and reporting outcomes
  • Addresses harms or occupational exposures
Other criteria
  • Original research studies that provide sufficient detail regarding methods and results to enable use and adjustment of the data and results
  • Studies with mixed patient populations must include ≥ 20 pregnant women in labor or provide extractable information addressing harms or occupational outcomes
  • Studies must include at least one outcome measure of an outcome listed in the PICOTS
  • Relevant outcomes must be extractable from data presented in the papers

From: Methods

Cover of Nitrous Oxide for the Management of Labor Pain
Nitrous Oxide for the Management of Labor Pain [Internet].
Comparative Effectiveness Reviews, No. 67.
Likis FE, Andrews JC, Collins MR, et al.

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.