The Duchess of York revealed her family's loss in an open letter

Sarah Ferguson told of the pain it had caused her family at the launch of the Stop Premature Births campaign.

The Duchess is patron of the charity Tommy's, which launched the drive because it said four babies die every day after being born prematurely.

In an open letter, the Duchess said her sister Jane had "suffered terribly" because of her loss.

'Not suffered'

The Duchess said: "Personally, I have been very fortunate and not suffered in the way so many parents have - but premature birth has touched my family."

She then quoted her sister Jane Ferguson, who said she had lost babies at 4.5, five, 5.5 and at 8.5 months.

It is indescribable Jane Ferguson

Jane recalled: "I distinctly remember holding Sophie and being told she would not live long.

"Not a day goes by, even today - and I have three wonderful children - when I do not ask someone why and how.

"The trauma of being in a maternity ward with other mothers who had their babies and then having to name and bury Sophie is something I will always live with.

"It is indescribable and only mothers who have been there will know the empty, hollow feelings you have and the utter desperation you feel that so many of your questions go unanswered."

The Duchess said that premature births were on the rise in the UK and that 50,000 babies were born too early each year.

Other celebrities who threw their weight behind the campaign included singers Jamelia, Kim Wilde and Kym Marsh, as well as with model Nell McAndrew, TV presenters Anthea Turner and Andrea Catherwood, and actors Amanda Holden and Richard E Grant.

Tommy's said premature birth kills more babies than any other cause.

Chief executive Jane Brewin said: "These figures will undoubtedly be distressing to many people - especially to those who are caring for or have lost a premature baby, and similarly to those parents bereaved by other causes of their baby's death."

The charity said it will fund research including into pre-eclampsia - a potentially fatal condition linked to high blood pressure.