The Sun reported that Doria, 62, is expected to touch down within days as her daughter Meghan, 37, plays host to her big bash.
It will take place at Frogmore House, the location that Meghan and her husband Prince Harry just moved into from Buckingham Palace.
Meghan enjoyed a star-studded baby shower in February that was attended by Serena Williams and Amal Clooney.
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Serena may have accidentally revealed the gender of Meghan and Harry's baby in a recent interview with E! News.
Victoria Beckham is reportedly set to attend Meghan's upcoming 2nd baby shower. She was at her wedding with husband David last May.
Doria is expected to stay in the UK in the run-up to the birth of the royal baby.