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Input: Princess Kate  pregnant with  her  third child  made  her  first public appearance in six weeks to join Prince William and Prince Harry at Buckingham Palace to mark World Mental Health Day.
 Kate   35  showed a slight baby bump beneath the tea-length Temperley dress  she  wore to the event  thanking supporters for helping to change public perceptions about mental health.
Kensington Palace announced  Kate 's pregnancy on Sept. 4 when she was forced to cancel a planned engagement as a result of hyperemesis gravidarum.  Kate  also missed the first day of school for  her  son  Prince George  a few days later.
 Kate  has suffered from hyperemesis gravidarum  or acute morning sickness  with each of  her  pregnancies. The palace announced that with this pregnancy   Kate  is being cared for at Kensington Palace.
The last time  Kate  was seen in public prior to today was in late August when  she  joined William and Harry in viewing the Diana Memorial Garden at Kensington Palace on the eve of the 20th anniversary of Princess Diana's death.
"The Duchess' condition is improving but she is still suffering from hyperemesis gravidarum " an aide to Princess Kate said today. "The Duchess is delighted to be here tonight."
William  Kate and Harry founded Heads Together in 2016 to change the conversation on mental health.
William told guests that it was Kate who first pointed out the royal trio's shared interest in mental health advocacy. They have each been engaged with their individual charitable work on the issue: Harry with the armed forces; William with young men  suicide and homelessness; and Kate on addiction and childhood mental health issues.
 William  Kate  and Harry  announced Sunday  they  have invested 2 million pounds of  their  Royal Foundation funds in the second phase of  their  Heads Together campaign  which is designed to create online tools to help people with mental health issues.

Princess Kate makes 1st public appearance since announcing her pregnancy