There is a relatively new (and not widely available) method of administering a narcotic for pain relief in labour called Patient Controlled Analgesia (or PCA). PCA involves the medication being placed into a syringe and attached to a special dispenser on a drip in the woman's vein.
The woman is given an initial small dose of narcotic through the vein (usually by an
anaesthetist) to relieve the pain, while they set up the apparatus. When the woman starts to feel pain again she periodically presses the button on the dispenser to give her a further small, measured dose of the medication. There is an inbuilt mechanism in the device that prevents the woman from overdosing on the narcotic, only allowing a precise dose to be given over a specified time frame.
The narcotic used can be pethidine, morphine or fentanyl (called 'Sublimaze'), a synthetic opiate. PCA would need to be turned down or off in the pushing phase of the labour to reduce the side effects of the narcotic on the baby.
You may wish to ask your caregiver if PCA is available for narcotic pain relief in your delivery suite. PCA would not be offered in a birth centre or at home because it is complex to administer and requires an anaesthetist to prescribe it, set it up and supervise it.