Can You Only Use Natural Baby Sponges To Bathe A Baby?

No, it isn't true. Synthetic sponges are just as good - I had a lovely synthetic baby sponge for my son when he was a baby. I would use a sponge that was designed for a baby - I would imagine that a normal synthetic sponge may be a bit tooo rough for baby delicate skin, but it doesn't have to be natural.