The tennis star, 35, made the announcement on Wednesday where she showed off her pregnant belly on Snapchat. Williams wore a yellow swimsuit and said she was 20 weeks along. The athlete is engaged to Reddit co-founder Alexis Ohanian, 33.
Serena had a small baby bump, which she showed in profile as she held up her phone to a mirror.
The suit had two gold buttons and a cut out on the side with narrow straps.
The beauty has been engaged to Alexis since December 2016. He proposed with a large diamond ring, which she showed off in January. They had been dating for only 15 months.