A source previously told Us Weekly that the monarch finds the term “vulgar”.
The insider told the magazine the Queen prefers to say “in the family way”.
Buckingham Palace announced last month that Beatrice is expecting a baby in the autumn.
The palace said the Queen’s granddaughter and Mr Mapelli Mozzi were “very pleased” to be welcoming their first child.
The palace added: “The Queen has been informed and both families are delighted with the news.”
Beatrice and Mr Mapelli Mozzi tied the knot last July in a secret lockdown wedding in Windsor after their planned ceremony was postponed due to the pandemic.
Beatrice’s younger sister Princess Eugenie welcomed a baby boy, called August, in February.
The sisters will be delighted to have their children so close together in age and to share the experience of being first-time mothers.
Their cousin Zara Tindall and her husband Mike welcomed her third child, named Lucas, in March.
The Duke and Duchess of Sussex, who are living in California after quitting royal duties, are expecting a daughter in the summer.
Beatrice is already stepmother to Mr Mapelli Mozzi’s young son Wolfie, from his previous relationship with his ex-fiancee Dara Huang.
The princess is the eldest daughter of Prince Andrew and Sarah Ferguson.
Her son or daughter will be 11th in line to the throne.
Beatrice is not a full-time working royal and is vice president of partnerships and strategy at Afiniti, an artificial intelligence software firm.
She has a number of royal patronages including the Forget Me Not Children’s Hospice, the Teenage Cancer Trust and the Helen Arkell Dyslexia Centre.
Source: EXPRESS CO UK