probably the opinion of one employee from a baby food producing company who had a marketing appointment with a paediatrician somewhere one day who mentioned something along the lines of 4 months and then it spread like wildfire - or maybe it was mentioned at a paediatric conference that was in some way sponsored by a baby food producing company - or maybe even an artificial baby milk producing company.

An MCHN will likely have gone to a different conference or had a visit from a different company rep so will likely tell something different.

Apologies if I sound jaded by the whole thing but I have seen and heard one too many a story to believe any paed or MCHN now... I stick with the WHO recommendations and they still stand at 6 months.