Duchess Catherine was spotted without her engagement ring, and now we know why

LONDON, ENGLAND - JANUARY 17: Catherine, Duchess of Cambridge arrives to officially open the Mittal Children's Medical Centre, home to the new Premier Inn Clinical Building at Great Ormond Street Hospital on January 17, 2018 in London, England. (Photo by Frank Augstein-WPA Pool/Getty Images)

Duchess Catherine made a public appearance this week without her engagement ring, but there was good reason to leave it behind.

The duchess visited young patients at the Great Ormond Street Hospital on Wednesday morning and decided to wear a simple gold band in place of her sapphire and diamond engagement ring due to the hospital’s strict policy on jewelry.

PEOPLE reports that the hospital requires visitors to thoroughly wash their hands prior to entering treatment areas, and it is recommended that all jewelry be removed.

Catherine left the sparkler at home and stuck with her simple wedding band when she visited the children and helped open the Mittal Children’s Medical Center.

Kensington Palace documented the duchess’s outing on Twitter for fans. She was met at the opening by 9-year-old patient, Ava, who greeted her with a shy smile and stuffed animal in hand.

RELATED: Duchess Catherine went into full mom-mode when a little boy got sick during her appearance

Catherine joined some of the patients for arts and crafts as she learned more about the impact the new center will have on them and their families.

At the end of the appearance, Catherine thanked the welcoming families and patients with a post on Twitter.

“It’s been wonderful to meet so many families and young people. I’ve been so inspired by their bravery and courage at such a difficult time,” she said to the crowd. “My main message is congratulations to all of you from the building perspective and also to all of the supporters in the room today. It means so much to the families, both to the parents and the children. You can see the real family unit that the hospital brings during these difficult times. Well done and huge congratulations, and I wish you the very best success in the future.”

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