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Pregnant with her second child, Duchess Kate is continuing to struggle with severe morning sickness. The illness is so bad that, unfortunately, it's even affecting her royal engagements.

On Wednesday, Kate was forced to cancel an appearance at the Clore Art Room at London's Barlby Primary School, as part of the Clore Duffield Foundation's 50th anniversary. The Oxford-based charity uses art therapy to help kids and teens with behavioral issues.

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"The Duchess of Cambridge continues to suffer from the effects of hyperemesis gravidarum and was unable to attend this event today in person. The decision to undertake engagements is being kept under review on a case-by-case basis," a Kensington Palace spokesman said.

All was not royally lost, though. In her absence, Prince William's wife sent an apology note to the center. "I wanted to share my congratulations with you all for the launch of the new Clore Art Room," she wrote in the letter. "I was looking forward to joining you all for this particularly special day as part of the Clore Duffield Foundation's 50th anniversary year."

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The heartfelt apology continued, "I am truly sorry that I cannot be with you all today as you celebrate this milestone. As patron of The Art Room, I feel great pride to see the work that the charity is doing. Vulnerable children flourish in the safe havens that The Art Room provides; this highlights just how important it is to support children at a time when they most need help and support."

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"It really is hugely exciting to look to a future with even more Art Rooms, where the lives of many more challenging and vulnerable children will be transformed," she wrote. "I hope that you have a wonderful afternoon. My sincere apologies for not being able to join you, but I hope that I will have an opportunity to visit Barlby and see the Clore Art Room soon."

The Duchess suffered similar symptoms while pregnant with Prince George, who is now 14 months old. Her current symptoms have forced her to bow out of several events, thus far, including an appearance in Oxford and one in Malta, which would have been her first individual royal tour.