"It is simply transformational," said Kate of the work carried out by those at the hospices. "There are 49 children's hospices services across the UK, all providing invaluable, life enhancing care to thousands of families."
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"Children's hospices provide lifelines to families at a time of unimaginable pain," she continued. "The support they give is vital."
"In order to carry out this wonderful work, our help is needed," said Kate, "It does not bear thinking about what these families would do without this."
More than a year after she announced her patronage for East Anglia Children's Hospices and gave her first solo speech at The Treehouse hospice, Kate will spend her second wedding anniversary visiting Naomi House hospice in Hampshire, during National Hospice Week.
"I hope you will join me this Children's Hospice Week in supporting your local service," said the Duchess of Cambridge as her message drew to a close. "With your support we can help ensure that these children and their families can make the most of the precious time they have together"
The video shows the pregnant Duchess wearing what appeared to be the Topshop dress she stepped out in for her visit to Child Bereavement UK in March. The on-trend black dress, with a Peter Pan collar, from Topshop's Tall section cost £42 and sold out on the company's website within the day.
Also visible in Kate's video is a framed photograph from her wedding to Prince William, significant as on Tuesday the pair will celebrate two happy years as a married couple. Pregnant Kate will spend the day away from her husband on 29 April as she visits Naomi House near Winchester in Hampshire, which was opened by Prince Charles in 1997.
The Duchess of Cambridge will be given a tour of the hospice, which comes exactly two years after her wedding ceremony at Westminster Abbey. During the visit, Kate will spend time with patients and their families and she will also meet volunteers and supporters of the hospice. The expectant royal is known for her work in the childcare sector and is a patron East Anglia's Children's Hospices.
After the tour, Kate will be treated to a royal tea party with some of the children and a musical performance by Ollie Wade, whose brother Ben passed away at the hospice in 2011. He will sing his own song Free, written in memory of his brother. The track will be available to buy from the beginning of Children's Hospice Week.
The Middleton family have connections with Naomi House. Their business, Party Pieces, previously hosted a Christmas party for the hospice's children.