First of all, he flip flopped a few times. Probably because he did do research, and at the time, it was all over the place. While his book was highly successful, many pamphlets that were handed out by pediatricians in the US, UK, and Australia, told parents to put their babies on their stomachs.

I am sure, in the light of half a century, many of the recommendations for infant health have changed. As a matter of fact, breastfeeding was considered a practice for those of the 'lower classes.' Hindsight ... 20/20.