Never accused of being anything less than entirely sensible, Kate Middleton—who is six months’ pregnant with her third child—has stopped wearing her famous engagement ring, in a move common among moms-to-be who may experience swollen fingers and have trouble removing jewelry during the later stages of pregnancy.

Cautious Kate appeared Wednesday at Britain’s top children’s hospital, the Great Ormond Street Hospital, where she was opening a new wing. She was photographed without her signature ring, according to the Daily Mail.

As one would expect of a princess whose husband has easy access to the world’s finest gems, Kate’s ring, which she usually wears, is a total whopper. It boasts a massive blue sapphire with an estimated value of some $400,000, and it was previously the property of Princess Diana.

At the time of his engagement to Kate, William said in an interview:  “It’s my mother’s engagement ring, so I thought it was quite nice because obviously she’s not going to be around to share any of the fun and excitement of it all— this was my way of keeping her close to it all.”

Pregnancy forums such as thebump.com regularly advise pregnant women to remove rings early on in their pregnancies: “I woke up in the middle of the night with very swollen fingers and my rings stuck on. Took awhile to get them off and was painful,” reads one typical post.

Some women say on online forums that they find their rings have to be resized after pregnancy, for those whose “fat fingers” stubbornly refuse to return to their former size.

As well as being uncomfortable, a stuck-on ring can be an issue if a mother requires a Caesarean birth, as most operating rooms forbid patients from wearing jewelry.

Kate met with staff and patients at the hospital opening, and was presented with a teddy bear by one young fan.