Objectives  To compare the efficacy of diamorphine administered by a patient-controlled pump (patient-controlled analgesia) with intramuscular administration for pain relief in labour.

Design  Randomised controlled trial.

Setting  The South Glasgow University Hospitals NHS Trust.

Sample  Primigravidae and multigravidae in labour at term (37–42 weeks).

Methods  Women were randomised in labour to the study (patient-controlled analgesia) or control group (intramuscular). Randomisation was achieved through a random permuted block design stratified by parity. Study group women were given a loading dose of 1.2 mg diamorphine intravenously and then attached to the pump. Control group women received intramuscular diamorphine as per hospital protocol. Participants were also given 3 mg of buccal Stemetil. Data were collected throughout labour and at six postnatal weeks.

Main outcome measures  Analgesia requirements during labour and women's satisfaction with the method of pain relief.

Results  Women in the study group (patient-controlled analgesia) used significantly less diamorphine than women in the control group (intramuscular) but were significantly more likely to state that they were very dissatisfied with their use of diamorphine and were significantly more likely to opt out of the trial before the birth of the baby. The majority of women in both groups used other analgesia concurrent with diamorphine such as Entonox, aromatherapy or TENS.

Conclusions  Patient-controlled analgesia administration of diamorphine for the relief of pain in labour offers no significant advantages over intramuscular administration. The results also suggest that diamorphine is a poor analgesic for labour pain irrespective of the mode of administration.