Marisa Miller may be pregnant, but that's not stopping her from showing off the body that made her famous!

The 34-year-old Sports Illustrated swimsuit model took to her Twitter yesterday, her birthday, to show off her curves -- which included her tiny baby bump.

"Thanks so much for all the sweet birthday wishes! Love you all! I had the best day and spent most of it under water," she said to her followers along with a pic of her swimming in a black bikini.

Miller announced her pregnancy in June. She's expecting her first child with husband Griffin Guess in the late fall.

Check out more bikini bods in the gallery above!