Best Beginnings, a charity which works to help parents give their children the best start in life, produced the films.
“Becoming a mother has been such a rewarding and wonderful experience,” she said during the speech.
“However, at times it has also been a huge challenge – even for me, who has support at home that most mothers do not.”
The Duchess continued: “Nothing can really prepare you for the sheer overwhelming experience of what it means to become a mother.
“It is full of complex emotions of joy, exhaustion, love and worry, all mixed together.
“Your fundamental identity changes overnight. You go from thinking of yourself as primarily an individual, to suddenly being a mother, first and foremost.
“And yet there is no rule book... You just have to make it up and do the very best you can to care for your family.”
Best Beginnings is a charity partner of the Duke and Duchess of Cambridge and Prince Harry’s Heads Together mental health awareness campaign.