why holding your baby is dangerous

I’m all for public service announcements that use a little shock value to raise public awareness, but this is a little much: 

You think the safest place in the world for your baby is wrapped in your arms.

But it can also be one of the most dangerous.

You hear that? Put your baby down! NOW! Leave her in her crib all day to atrophy, like Madame Bovary would have. Now there was a good mother.