Intended for healthcare professionals


Six months of exclusive breast feeding: how good is the evidence?

BMJ 2011; 342 doi: (Published 13 January 2011) Cite this as: BMJ 2011;342:c5955

Room for a cluster RCT?

Looking at the call for large randomised controlled trials made by
the Cochrane Review on this topic
and at the feeding recommendations made by the British Dietetic
Association under Reference 34
I wonder if there might not be room for a cluster randomised controlled
trial in a developed setting of something like the following two sets of

1) The WHO advice, that exclusive breastfeeding be carried out to at
least 6 months;

2) The BDA advice, that term infants should begin weaning at 4-6 months,
but pre-term at 5-8 months, with the precise age depending on
consideration of the individual infant.

However, in suggesting such a trial, I'd be uncertain about the

1) What primary outcome would be best? All-cause mortality from 4 months
onwards would be far too rare an outcome with too small a predicted effect
in a developed setting for anything but a huge trial. The number of
hospital admissions would enable slightly greater power, perhaps, although
the predicted effect of intervention would also be very small and you'd
also want to look at a long list of secondary outcomes for both mother
(weight loss; satisfaction with feeding advice; ability to follow it;
proportion completing at least 4 months breastfeeding; mean age of
beginning to wean and mean age of complete weaning) and baby (all-cause
mortality; weight; length; risk of anaemia; risk of zinc deficiency; risk
of food allergy; risk of childhood obesity etc.).

2) How long should you follow patients up for?

3) At what level should you randomise? (GP practice?)

4) Might sending mixed messages confuse people as to what is really best?

Competing interests: No competing interests

17 January 2011
Patrick W Woodburn
Medical student
Barts and the London