She's Back! Princess Kate Debuts Baby Bump at First Appearance Since Announcing Her Pregnancy

After battling severe pregnancy sickness for the past month, Kate Middleton is stepping out for the first time since announcing she is expecting her third child.

On Tuesday, the royal mom joined her husband, Prince William, and brother-in-law, Prince Harry, to celebrate World Mental Health Day at a special Buckingham Palace reception to honor supporters of the royal trio’s Heads Together campaign, which aims to reduce the stigma surrounding mental health issues.

An aide told reporters, “The Duchess’ condition is improving but she is still suffering from Hyperemesis Gravidarum. She is delighted to be able to be here tonight.”

Bump just visible as Kate makes her first appearance since her third pregnancy is announced http://pic.twitter.com/5NuTp9swdr

— Victoria Murphy (@QueenVicMirror) October 10, 2017

The royal mom walked into The White Drawing Room with William and Harry in a pretty blue Temperly dress, which showed off a hint of a baby bump.

Kate and William at #WMHD17 reception at Buckingham Palace this evening http://pic.twitter.com/xVgvfcWKr8

— Simon Perry (@SPerryPeoplemag) October 10, 2017

The event marked Kate’s first public outing since August 30, when she and the royal brothers marked the 20th anniversary of the death of Princess Diana. Only a few days after that, it was announced that she is pregnant – and with that came news she was suffering from Hyperemesis Gravidarum, an extreme form of morning sickness that forced her to cancel her public duties.

The illness also meant  that she missed taking her 4-year-old son Prince George to his first day of school last month. (William pulled solo dad duty instead, later saying that most parents were “in floods of tears. The kids were all fine.”)

Early on Tuesday, William and Harry attended a party at St. James’s Palace, where they were praised by those in the mental health community for their work to break down stigmas surrounding issues of anxiety, depression and more.

Today, #WorldMentalHealthDay, is a chance to thank say thank you to everyone who supported the @heads_together campaign http://pic.twitter.com/DnTNTOR3wu

— Kensington Palace (@KensingtonRoyal) October 10, 2017

In a speech, William thanked everyone for what they’d done and said it was Kate “who first realized that all three of us were working on mental health in our individual areas of focus. She had seen that at the core of adult issues like addiction and family breakdown, unresolved childhood mental health issues were often part of the problem.”

Harry said it was time to take the awareness to the next stage and take it into “new partnerships to support better conversations in schools and workplaces.”

Writer and activist Fiona Millar told PEOPLE that William touched upon shifting attitudes among younger generations on the subject of mental health.

“He was saying about people in the Great War not wanting to talk about their emotional experiences, and then passing it on to their children — the stiff upper lip, ‘Don’t talk about how we feel,’ ” says Millar. “To be perfectly honest, that is a bit of a trademark of the royal family. And it obviously has its place. But the fact that they came out and did talk so openly about their feelings was a real shock to a lot of people. They don’t expect the royals to do that.”

Philippa Creasy, who lost her husband Terry to suicide five years ago, says the royals “undoubtedly” can take the issue of mental health forward: “They’re the only three who can do it. No one could change the conversation like they’ve done.”