Effectiveness of individual midwives is unclear

EDITOR—I should like to comment on the randomised controlled trial of midwife led debriefing to reduce maternal depression by Small et al.1 The first randomised clinical trial was of a drug treatment, streptomycin for pulmonary tuberculosis,2 which has provided the model for clinical trials ever since. In a drug trial we are not usually concerned with who is giving the drug because the effect of the drug itself is being measured. The treatment is impersonal, and we should be justified in assuming that the effect of a drug given by one person will be the same as it would be given by another.

When we carry out trials of more personal treatments, however, as in the trial by Small et al, we should be aware that the treatment given by one operator might not be the same as that given by another. Surgeons are not all equally skilful, for example. So if we were to carry out a trial comparing two surgical techniques the surgeons would be a non-random sample from the wider …