I like the nickname, don't like the full name?

I like the nickname Cindy but I don't like the full name Cynthia. It just doesn't sound very pretty (I don't even want it on the birth certificate). Besides, it makes me think of that ugly doll on The Rugrats. I notice that a lot of older women that have the name always go by Cindy. Do you think it would be ok to put Cindy as the full name on the birth certificate? Does Cindy sound too much like a nickname? Should I just choose a different name? It's probably not a good idea to put a nickname on the birth certificate. Maybe you should try to convince me that Cindy isn't a pretty name either :)