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Middlesex-London Health Unit

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Narcotic Pain Medications

Opioid analgesics, or narcotics, are a class of pain medications which includes many different drugs with different strengths, speed of onset, durations, and side effects. They are usually used to treat moderate to severe pain.

The following information will assist you to make an informed decision about the use of narcotic medications for pain relief in labour that is in line with your preferences and values. It’s important to learn about the benefits, risks and alternatives before labour begins. The following are population level benefits and risks. In order to make an informed decision, it's important to speak with your healthcare provider to discuss how these may apply to your individual situation.



  • May provide effective pain relief
  • May be administered quickly in early labour
  • Does not get rid of pain but makes it seem less intense


  • Nausea (feeling sick to your stomach)
  • Vomiting (throwing up)
  • Dry mouth
  • Constipation (having trouble or not able to pass stool)
  • Urinary retention (having trouble or not able to pass urine)
  • Itchiness
  • Dizziness/weakness
  • Sleepiness/drowsiness
  • Hallucinations (seeing or experiencing something that is not there)
  • Decreased ability to safely move around on your own
  • Low blood pressure
  • Fast or slow heart rate
  • Maternal respiratory depression (slowed or shallow breathing)
  • Decreased fetal heart rate and/or decreased fetal heart rate variability
  • Fetal or newborn sedation (sleepiness) and/or respiratory depression (slow or shallow breathing)
  • Incomplete pain relief
  • Delayed start to breastfeeding

Please note that all narcotics cross the placenta and take more time to be get out of the baby’s circulation than the mothers.  There is an increased need to assess the baby at birth. The Neonatal Intensive Care Unit (NICU) Team will be called to the birth if the baby shows signs of needing respiratory assistance (help with breathing) or if the narcotic was given within 4 hours of birth.


There are a variety of coping techniques you can use to manage the pain you experience during labour. Comfort measures do not involve the use of medications for pain relief. They allow you to have a better sense of control, can result in a shorter labour with fewer medical interventions. Using comfort measures to avoid unnecessary interventions also supports your birth hormones. This will help you to have a labour that feels less intense and progresses more quickly. It also sets you up for better breastfeeding success. There is also no risk for you or your baby. See our Comfort Measures webpage for more information.


Narcotics can be given by an intramuscular (IM) injection or an intravenous (IV) infusion. The route is often determined by the type of narcotic as well as the stage of labour.

Intramuscular Injections

During labour, you can receive narcotics for pain relief by an injection given in your upper arm muscle, upper thigh muscle, or gluteal (buttock) muscle. This is called an intramuscular (IM) injection. This form of medication will last from 2 to 4 hours.
Advantages of receiving pain medication by an IM injection include:

  • Can be given quickly
  • No need for an Intravenous (IV) line

Disadvantages of receiving pain medication by an IM injection include:

  • Delayed pain relief compared to intravenous (IV) infusion
  • The need for high doses of medication
  • An unpredictable rate of release of medication from muscle tissue that can result in uneven distribution of the medication
  • The inability to give medication close to birth with this method. There may not be enough time for the medication to get out of the baby’s circulation before birth, this can lead to sedation (sleepiness) and/or respiratory depression (slowed or shallow breathing).

Intravenous Infusion

During labour, you can receive narcotics for pain relief by Intravenous (IV) infusion called patient-controlled analgesia (PCA). For this, an IV pump is programmed to allow you to push a button to give yourself a small dose of a narcotic (e.g. fentanyl) when needed. Most of the time there is also a constant, small amount of medication given and you top this up as needed. An IV PCA allows you to have more control of pain management during labour. It is also sometimes reserved for women who cannot get an epidural.
Advantages of receiving pain medication by IV (compared to IM) include:

  • Starts working sooner than intramuscular (IM) injections
  • Smaller doses of medication
  • A more predictable effect

Disadvantages of receiving pain medication via an IV, (compared to IM) include:

  • Restricted movement due to the IV set-up.

For more information, decision aids & tools:

If you have specific questions:

  • Speak with your healthcare provider
Date of creation: February 20, 2015
Last modified on: June 4, 2019


1Middlesex-London Health Unit & London Health Sciences Centre (2014). Birthing at London Health Sciences Centre. Retrieved from
2Best Start Resource Centre. (2016). Pain Medications in Labour. Retrieved from
3National Collaborating Centre for Women's and Children's Health (UK). (2014). Intrapartum care: Care of healthy women and their babies during childbirth - Chapter 8: Coping with pain in labour-non-epidural. Retrieved from