Sheikh `Abd al-Wahhâb al-Turayrî, former professor at al-Imâm University in Riyadh
There is nothing in Islam specifically prohibiting this practice. Therefore, it would be permissible for a Muslim woman to have her navel pierced as long as it is considered an accepetable form of adornment by people in the region of the world in which she lives. However, this permission is conditional on there being no ensuing harm on the body.
Basically, body piercing takes the same ruling as piercing the nose or ear takes in the Muslim countries where the practice of piercing the ear or nose is quite common.
And Allah knows best.
Source: Islam Today