The Duchess of Cambridge has praised the country's midwives for their "amazing work bringing new life into our world" in an open letter to the profession.
Kate tells midwives their work is of "fundamental importance" to the early years development of children - an issue she has been raising awareness about for a number of years.
The duchess has revealed she took part in home visits with midwives during two days spent shadowing staff at Kingston Hospital's maternity unit in London in November.
Four pictures showing her time with workers have been released by Kensington Palace, and in one image Kate is pictured crouching over a baby in a cot as the infant's parents watch, while in others she is seen meeting staff.
In the letter, published ahead of the start of 2020 designated Year of the Nurse and Midwife, Kate said: "You are there for women at their most vulnerable; you witness strength, pain and unimaginable joy on a daily basis. Your work often goes on behind the scenes, and away from the spotlight.
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"Recently however, I was privileged enough to witness a small section of it first hand, spending several days at Kingston Hospital's maternity unit.
"Although this was not my first encounter with the care and kindness provided by midwives across the country, it gave me a broader insight into the true impact you have on everybody you help."
With three children under the age of seven - Prince George, aged six, Princess Charlotte, aged four, and Prince Louis who is 20-months-old - Kate is focused on improving the early years support for children and their parents.
She has established a steering group of experts, which first met in May 2018, to look at the issue and they have been considering how the duchess and her Royal Foundation can help improve outcomes for youngsters.
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The experts have been looking at preparations for parenthood, pregnancy, and a child's early years and Kate is likely to build on their work next year.
Kate tells the midwives in her letter: "The help and reassurance you provide for parents-to-be and parents of newborns is just as crucial. It goes a long way in building parents' confidence from the start, with lifelong impact on the future happiness of their children.
"The early years are more critical for future health and happiness than any other moment in our lifetime. Even before we are born, our mother's emotional and physical health directly influences our development and by the age of five a child's brain has developed to 90% of its adult size.
"Your role at the very start of this period is therefore of fundamental importance."
The Princess Royal has also been supporting members of the medical profession for many years and is involved with a number of professional bodies, acting as patron of the College of Paediatrics and Child Health, and she is an Honorary Fellow of the Royal College of Obstetricians and Gynaecologists.
In the letter, which will be posted on the Royal College of Midwives' website, Kate goes on to say: "The founder of modern nursing, Florence Nightingale - whose 200th anniversary we celebrate next year - once said, 'I attribute my success to this: I never have or took an excuse' and it is that mantra that I have seen time and time again in all of my encounters with you.
"You don't ask for praise or for recognition but instead unwaveringly continue your amazing work bringing new life into our world.
"You continue to demonstrate that despite your technical mastery and the advancement of modern medicine, it is the human to human relationships and simple acts of kindness that sometimes mean the most."