I did a search on this topic before, I think the conclusion is that it is alright. I I remember reading that one opthalmologist commented that the lights they shine into babies' eyes are very bright too, and for much longer than a flash's duration.
But no damage doesn't mean that the babies will like it. I certain don't like being flashed at as the 'hotspot' remains in my vision for a while.
I always use bounce the flash off the ceiling or walls when shooting babies. I don't even use a diffuser. No matter what the experts may say, it could upset the baby a lot. I remember my first flash shots when shooting a friend's 3-month old son. The poor chap looked absolutely shocked when the flash went off. Started crying. Some babies are OK. My daughter was no trouble at all, but I still use bounce flash.