Queen Elizabeth II's eldest granddaughter, eventing champion Zara Tindall, and her rugby player husband Mike Tindall are expecting their first child at the beginning of next year, Buckingham Palace announced on Monday.

The couple married in July 2011, three months after Tindall's cousin Prince William and Catherine, and announced their pregnancy just days before the second-in-line to the throne is expecting his first child.

"Mr and Mrs Mike Tindall are very pleased to announce that Zara Tindall is expecting a baby in the New Year," Buckingham Palace said in a statement.

Tindall, formerly Zara Phillips, is 32 years old and a former equestrian world champion.

She is the second child of the queen's daughter Princess Anne, the Princess Royal, and Mark Phillips. Her parents are divorced.

Her husband is a former England centre, although he has not played for his country since the team's woeful performance in the 2011 Rugby World Cup.

He made global headlines after being filmed flirting with an old flame in a bar during the tournament, just weeks after his wedding.

"The Princess Royal and Captain Mark Phillips, Mr Phillip and Mrs Linda Tindall, and members of both families are delighted with the news," the palace statement said.

"This baby will be the first child for Mike and Zara and the third grandchild for the Princess Royal."

Tindall's brother Peter Phillips is married to Autumn and they have two little girls, Savannah and Isla.

The announcement of her pregnancy is likely to be overshadowed by the global frenzy over William and Catherine's baby, which is due within days.