Fergie: Good Genes or Good Docs?!

Fergie's beauty is "Boom Boom Pow!"

Here's a 28-year-old version of the The Black Eyed Peas singer turned solo artist in Los Angeles back in 2003 (left) and 12 years later ... the mother of one -- who turned the BIG 4-0 earlier this week -- relaxing at a fashion event sans eyebrow piercing earlier this year (right).