Tennis star Serena Williams 'gives birth to baby daughter'
Reports star had given birth came moments before her sister Venus took centre court at the US Open.
Serena Williams has given birth to a baby girl, according to widespread reports.
The US Open tweeted a video message of congratulations to the tennis star at the news.
It comes a day after reports Serena, 35, had gone into labour at St Mary's Medical Centre in West Palm Beach in Florida.
It was also moments before Venus took centre court at the US Open for her third-round match against Maria Sakkari.
Serena's fiance, Alexis Ohanian, the founder of Reddit, said in August he believed the 23-time grand slam champion would make an "awesome" mum.
Stacey Allaster, chief executive of the US Tennis Association said: "Hey Serena, welcome to the best club in the world: motherhood. Can't wait to see you, a mum, and your precious little healthy baby. Congrats!"
Spain's tennis superstar, Rafael Nadal also tweeted: "Congrats Serena!!! So much joy for you!!!"
Last month Serena, whose coach says the star plans to compete in the Australian Open in January, hosted a 50s-themed baby shower.
Among the stars who attended the party were Eva Longoria, Ciara, Destiny's Child star Kelly Rowland and La La Anthony.