Phillips, 32, an Olympic equestrian, married rugby star Mike Tindall in 2011 in Scotland just a few weeks after Prince William married Kate Middleton.
According to the release, "both families are delighted with the news."
Phillip's baby will be her first child with her husband and the third grandchild for Princess Anne.
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Zara Phillips Tindall, daughter of Princess Anne, is pregnant and due to give birth in early 2014, Buckingham Palace
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