The Duchess of Cambridge is expected to give birth in July to her first child. The actual due date has not been announced, but the media are assuming that the birth will take place in mid-July.
This year Queen Elizabeth II will celebrate the 60th anniversary of her Coronation. The actual date of the Coronation is June 2. However, a major celebration is to take place at Buckingham Palace from July 11 through July 14.
A "Spectacular Evening Gala" will take place on the evenings of July 12 and July 13. These would not be the right times for Prince William to be rushing Catherine to the hospital.
I think we can safely assume that Catherine will not be present at these events whether she already has given birth or is in the final days of her pregnancy.
This also means Baby Cambridge will be getting more attention than the Coronation anniversary celebrations.