Wearing a bright yellow costume‚ Serena posted a picture to SnapChat and used the caption “20 weeks.”
The image has since gone viral.
Williams, 35, hasn’t played since beating her sister Venus in the final of the Australian Open in January to clinch a record 23rd Grand Slam singles title.
She cited a knee injury in pulling out of tournaments in Indian Wells and Miami in March.
In December she announced her engagement to Reddit co-founder Alexis Ohanian, first sharing that news on the Reddit social media site.
This will be the couples first child together.
Of course the internet has already gone crazy about the news.