"He said they shouldn't call it morning sickness as it's a day and all night sickness," O'Higgens said.
William told guests that some of the "most inspiring moments of my life" had been with the young people of Centrepoint, of which he is a patron.
He recalled spending a night on the streets in 2009 to experience what it was like sleeping rough.
"I was cold but safe, and I knew I had a home waiting for me," he said.
"Many others have no such luck. The cold streets are the only reality they know.
"And yet so often their spirit shines through.
"What these unfortunate men, women and young people could achieve given the right opportunities is limitless, I really believe that."
Guests were also treated to a tennis match between former British number one Tim Henman and Croatian Goran Ivanisevic.
The game was won by Henman, with showman Ivanisevic clowning around throughout the match.
The event ended with William presenting the Centrepoint Great Britain Youth Inspiration Award to Novak Djokovic.
The world number one, who is a UNICEF ambassador, was recognised for his humanitarian work to raise awareness of the importance of early childhood education in his home country of Serbia.
-AAP
