Bump in St. Bart's!

Third-time mom-to-be Uma Thurman proudly showed off her growing baby bump in a black bikini in St. Bart's over the weekend. (See more pix at X17.)

The Kill Bill actress and former model, 41, hit the surf and hung out in the sand with Maya, 13, her daughter with ex-husband Ethan Hawke.

Us Weekly broke news in February that Thurman was pregnant again; the dad-to-be is Arpad Busson, her financier beau, with whom she reunited last year.

In addition to Maya, Thurman and ex Hawke have a 10-year-old son, Levon. Hawke himself has two younger daughters -- Clementine, 3, and Indiana, 6 months -- with second wife Ryan Shawhughes, whom he married 2008.

Thurman costars with Robert Pattinson in period drama Bel Ami, which hits theaters later this month.