54-Year-Old Brigitte Nielsen Announces She's Pregnant

Brigitte Nielsen has already proven age ain't nothing but a number with her stunning beauty ... but she just took it to a whole new level by announcing she's pregnant at 54!!

Sylvester Stallone's ex took to Instagram to announce she's pregnant with her 5th kid ... posting this picture in a white getup and holding her rather large baby bump. She captioned the pic,"family getting larger #me #family #brigittenielsen #babybump."

Brigitte -- who played Ivan Drago's wife in "Rocky IV" -- has 4 sons -- Julian (34), Killian (28), Douglas (25) and Raoul (23) -- but none with Stallone.