In the UK,
Pearl is predominately used for older women, although I have seen it recently for a baby girl - jewel names i.e.
Ruby,
Amber etc are popular at the moment, so it may well be the beginning of a revival for this name!
Rhiannon is a very popular name in the UK, especially amongst Welsh people, at the moment. I love it, and its alternate form
Rhianna. I would pronounce it as ree-ann-en