The Duchess of Cambridge thanked the midwives for showing her their work behind the scenes

Kate Middleton wrote a touching letter to midwives following her secret visit to a maternity ward at a London hospital last month.

“You are there for women at their most vulnerable; you witness strength, pain and unimaginable joy on a daily basis,” the royal mom of three wrote in a letter that begins “Dear Midwives” and is signed “Catherine.”

Kate’s visit comes as the World Health Organization (WHO) has designated 2020 as designated the “Year of the Nurse and Midwife” in honor of the 200th birth anniversary of the founder of modern nursing, Florence Nightingale.

In the letter, which was released by Kensington Palace, Kate praised the professionals for their “behind-the-scenes” work that goes on away “from the spotlight.”

Catherine, Duchess of Cambridge letter to midwives
Kate Middleton’s letter for International Year of the Nurse and Midwife (part one).
| Credit: Kensington Palace
Catherine, Duchess of Cambridge letter to midwives
Kate Middleton’s letter for International Year of the Nurse and Midwife (part two).
| Credit: Catherine, Duchess of Cambridge letter to midwives

“During my time at Kingston I accompanied community midwives on their daily rounds and was welcomed into people’s homes,” she continued. “I was truly touched by the trust that people placed in me, sharing their experiences and voicing their fears openly. I also spent time in hospital clinics and on post-natal wards.

“No matter the setting, I was continually struck by the compassion that those of you I spent time with showed, and the incredible work ethic you demonstrated on behalf of your entire profession — not only performing your rounds but working tirelessly through the night to support people that were at their most vulnerable,” she added.

She wrote, “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.”

The royal said that the work nurses and midwives do in supporting the “critical phase of development” of children and moms “extends far beyond the complicated task of delivering a baby successfully. The help and reassurance you provide for parents-to-be and parents of newborns is just as crucial.”

Catherine, Duchess of Cambridge
Kate Middleton
| Credit: Samir Hussein/WireImage

Kate, 37, added, “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 5 a child’s brain has developed to 90 percent of its adult size. Your role at the very start of this period is therefore of fundamental importance.”

Kate is determined to make a difference for children, parents and caregivers and has made the early years the focus of her public work. A steering group of professionals has been advising her and concluded its work last spring. In the coming months, that exploratory work will start to be put into action.

Thanking the group for their guidance, Kate said in May, “I hope my long-term commitment to working in the early years will help make a difference over a generational timescale. Your thoughts and advice will continue to be hugely valuable as I shape my thinking for the years ahead.”

Can’t get enough of PEOPLE‘s Royals coverage? Sign up for our free Royals newsletter to get the latest updates on Kate Middleton, Meghan Markle and more!

David Holmes, CEO of one of her charities, Family Action, and a member of the steering group, told PEOPLE earlier this year: “She has a really deep interest in the early years and parenting and families.”

“Being a parent changes your life so much,” he said. “It’s great that she’s using her own experience and is interested in an area which is such a shared experience for so many.”