Serena Williams, 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, which means she won the Australian Open in late January at around 8 weeks.
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.