The 2009 Horse of the Year is in foal with an expected due date of Feb. 1, 2012.
Stonestreet Farm announced the pregnancy Monday, two weeks after the 2009 Preakness winner was bred to two-time Horse of the Year winner and stablemate Curlin.
The two horses mated in a breeding shed at Lane's End Farm, near Versailles, Ky., on Feb. 21. The gestation period takes almost a year, with the earliest chance to find out the gender coming at around the two-month mark.
Owner Jess Jackson was not available for comment, but he's been anticipating getting two of racing's biggest names together since he purchased Rachel Alexandra days after her record run in the 2009 Kentucky Oaks.
He has said any future offspring from the two stars might produce a "super horse." His wife, Barbara Banke, called it a "privilege" to bring the two greats together.
Rachel Alexandra captured 2009 Horse of the Year honors in spectacular fashion, becoming the first filly in more than 80 years to win the Preakness, then backing it up with wins in the Haskell and the Woodward. It was all part of an 8-0 campaign.
She struggled regaining her form in 2010, winning just two of five races. Jackson retired her in September, saying it was time to "reward her with a less stressful life."
There was little doubt her first chance at becoming a broodmare would be with Curlin. The 2007 and 2008 Horse of the Year, a Preakness winner in his own right, stands for $40,000 at Lane's End after a brilliant career in which he set a North American record by winning more than $10.5 million in purses.