The four-time Cox Plate winner was sent to Yarraman Park Stud at Scone for the 2019 breeding season where she was due to create a future champion with local sire I Am Invincible.

The ownership group of the Kepitis, Tighe and Treweeke families made the announcement today confirming with great sadness her foal had been lost overnight.

"There are so many people involved in the Winx story from owners, staff past and present to her many fans around the world.

"Our thoughts and attention at the moment are on Winx ensuring that she remains healthy, as anyone in this situation would respect.

"It is a traumatic time for a mother and those involved and Winx is now the centre of our attention following the loss of a beautiful filly this morning.

"We wish to thank everyone for their support and understanding, please respect the connections during this sad time and we will update you as soon as appropriate."

The Chris Waller-trained Winx was retired after winning the Queen Elizabeth Stakes at Royal Randwick on day two of The Championships in April last year.

Rated the world's best racehorse in 2018, the wonder mare was unbeatable for nearly four years, ending her racing career with 33 consecutive wins and a world record 25 at Group 1 level.