Letters written by the Queen to her midwife have gone on display before they are auctioned on Monday.
Sister "Rowie" attended the births of all four of the Queen's children
Sister Helen Rowe, known affectionately by Her Majesty as Rowie, attended the births of all four royal children.
The lots, which include photographs, have gone on view at Bonhams in Bath before going under the hammer.
The five hand-written letters, dating from 1959 to 1964, give a rare insight into the Queen's private life as she discusses her young children.
An extract from one, concerning the imminent birth of Prince Andrew, reads: "The children were very excited at the news of the baby, especially Charles who loves small children."
Gill Atkins from Bonhams said: "They are letters you would imagine any proud young mother would write to somebody who knew the children and it charts particularly the progress of Charles and Anne."
The letters, which appear in the same lot, are expected to fetch between £400 and £800.
Sister Rowe, who died in 1966, also kept many other mementoes and letters sent to her by other members of the Royal Family.
One letter, written by Prince Philip and sent from HMS Magpie, thanks her for "ably looking after the two Princesses".