Speaking to mark the Together for Short Lives' Children's Hospice Week, the expectant princess talks of the "remarkable work" that one of her key charities, East Anglia's Children's Hospices [EACH], does for children and their families.
"Children's hospices provide lifelines to families at a time of unimaginable pain," she says in the two-minute video that was recorded at Clarence House, London.
Urging help, she adds, "It does not bear thinking about what these families would do without this."
Children's Hospice Week is organized by Together for Short Lives, a UK charity for children and young people with life-limiting conditions and for those who love and care for them. Kate plans to visit a hospice in Hampshire, England, on Monday.
It comes amid an intensive period activity for her.
Last week, as she stepped out for her charity The Art Room at The National Portrait Gallery and joined husband William and brother in law Prince Harry at the Harry Potter studios, she also made a landmark speech about addiction.