Obstetric analgesia

Non-pharmacological treatment

Non-drug options available to women in labour, include prepared childbirth training, TENS therapy and physical therapy. Women should be given a realistic assessment of the severity of labour pain and the relative efficacy of non-pharmacological methods; for example, prepared childbirth training reduces labour pain by only about 10 per cent.

Pharmacological treatment

Pain in childbirth is frequently severe, being rated by many women as the most painful experience of their lives. Options for effective analgesia should be made available to all women in labour. Most women request pharmacological analgesia and there is a variety of agents and methods of administration.

These include:

• Inhalation of nitrous oxide and oxygen. The analgesic effect is limited, but can be helpful. Nitrous oxide combined with oxygen alone has no effects on neonatal neuro-adaptive capacity or Apgar scores. A combination of opioids such as pethidine and nitrous oxide combined with oxygen can produce maternal (and thereby foetal) hypoxaemia. Such episodes appear to be of doubtful clinical importance as they are transient and are followed immediately by periods of hyperoxaemia.
• Pethidine and other opioids administered by injection. Fentanyl, morphine and pethidine are suitable, with fentanyl producing less nausea and sedation and a faster effect. Pethidine (and other opioids) administered via the intramuscular route are very commonly used but their analgesic effect varies widely among patients.
• Epidural administration of opioid and local anaesthetic. Epidural analgesia is a highly effective method of relieving labour pain, allowing titration and individualisation of dose to pain intensity and usually avoiding motor block. Most epidural techniques today use a combination of low doses of opioid and local anaesthetic (eg lignocaine with or without adrenaline as a test dose followed by bupivacaine or ropivacaine). The dose may be increased to allow instrumental vaginal delivery and other procedures to be carried out. Intravenous fluids should be given as required during epidural analgesia, after routine ‘pre-loading'.

Women should be informed of the potential adverse effects of analgesia.

Adverse effects of epidural analgesia include:

• motor blockade leading to diminished mobility and ability to push during the second stage;
  
• bladder distension;
  
• diminished awareness of uterine contractions;
  
• postural hypotension;
  
• side effects related to epidural opioids (eg respiratory depression, pruritus, nausea);