Serena Williams has hinted she is 20 weeks pregnant, which would mean the American tennis champion was pregnant when she won the Australian Open less than 12 weeks ago.

Wiliams, 35, who is engaged to Alexis Ohanian, the co-founder of social news aggregation and discussion website Reddit, posted a picture of herself in a yellow bathing suit to Snapchat on Wednesday.

The photograph, which showed a slight bump at her stomach, was captioned "20 weeks".

Neither Williams or Ohanian have made any further comment.

On January 28, Williams defeated her sister Venus to win the Australian Open, her 23rd singles major and seventh Australian title.

Williams and Ohanian announced their engagement in December 2016.