Italy is introducing legislation making it illegal for girls under 18 to have breast enhancement or other plastic surgery. No such law exists in England, according to the Telegraph UK.
Looking for information about the US, it seems that breast implants are illegal for women under 22.
In 2008, more than 300,000 breast enlargements were done with silicone or saline implants and almost 80,000 breast cancer patients had reconstruction after mastectomy, often with implants. The popularity of breast augmentation has more than tripled since 1997, when there were just over 101,000 of these procedures. Read more