Ilie Nastase was heard making the racist comments at a press conference
Racist comments were heard regarding Serena Williams' pregnancy, on the eve of the Fed Cup play-off between Romania and Great Britain.
Romanian captain Ilie Nastase is believed to have made the slur at a press conference ahead of the event, when a microphone picked him up as saying:
"Let's see what colour it has. Chocolate with milk?"
Williams announced this week that she is 20 weeks pregnant with her fiancé, Alexis Ohanian, who is white. The timing of her announcement means that she was eight weeks pregnant when she won the Australian Open, leading to widespread praise of her athletic abilities.
Romanian player Simona Halep was fielding a question regarding Williams' pregnancy at the Fed Cup draw yesterday, when the 70-year-old Nastase turned to one one of his team members and added the above comment in Romanian.
The International Tennis Federation (ITF) told the BBC it is aware of the comments and has begun an immediate investigation.
A statement from the ITF reads:
"The ITF does not tolerate discriminatory and offensive language and behaviour of any kind."
This is the second time that Nastase has made controversial comments about the reigning Wimbledon champion. In March, he made unsubstantiated allegations of doping against Williams, based on her physical appearance.
The Romanian website Digisport.ro, quoted him as saying: 'Don't you see how she looks like?'
Nastase is a former world number one tennis player and Grand Slam champion.
Great Britain and Romania start their two-day World Group play-off tie today.