British tennis star Anne Keothavong and Serbian Ana Ivanovic were among the players at the event.
Keothavong, 25, wore a sparkling gold gown which flattered her athletic figure, while 21-year-old Ivanovic showed off her figure in a black and gold prom dress.
She started jumping up and down, saying, 'Oh, my baby is having a baby!
It's made our home have this lovely feeling about it."Heidi also revealed that her mother was one of the first people she told, recalling: "I wanted to be sure before I told her so I made Alex go out to buy another test."I gave him the stick to check this time and he told me we were having a baby.
I then went downstairs and put it on the kitchen counter in front of my mum.
It's made our home have this lovely feeling about it.'Heidi and 37-year-old Alex don't yet know the sex of their unborn baby but are planning a gender reveal party to celebrate with their loved ones in the coming weeks.
Heidi and Alex were set up by her personal trainer in early 2014, and felt and instant connection.
'It's the sort of kit only former Wimbledon champions can wear and keep a straight face, but at 27, Serena has every reason to boast.