Engaged to dad-to-be Olivier Martinez, Berry completed the look with diamond-drop earrings and silver accessories.
Halle, 46, told CNN on Monday about the pregnancy, "This has been the biggest surprise of my life, to tell you the truth. Thought I was kind of past the point where this could be a reality for me. So it's been a big surprise and the most wonderful."
The baby will join big sister Nahla, Berry's 5-year-old with her ex-boyfriend, model Gabriel Aubry.
Actress Halle Berry is simply glowing with impending motherhood!
The Oscar winner, in Buenos Aires promoting her thriller “The Call,” looked stunning in a regal, one-strapped purple gown, caressing her growing belly.