George and Charlotte better make room for a sibling!

Kate Middleton debuted her baby bump in a light blue dress on World Mental Health Day alongside husband Prince William and brother-in-law Prince Harry on Tuesday, and it's nice to see that the princess is feeling well enough to make a public appearance.

She has been suffering from severe morning sickness, as she did with her other two pregnancies, but she put on a brave face for a cause very close to her heart. Kate, William, and Harry have headed up the Heads Together campaign, which aims to reduce the stigma surrounding mental health issues.

No word yet on the couple's third child's due date or gender, but we wouldn't be surprised if she's dropping a tiny hint with this outfit and it's another boy!

We wonder if Harry and Meghan Markle will go public with their engagement before this baby is born?