The reason Kate Middleton has been spotted without engagement ring on is all down to her third pregnancy!

Kate Middleton has been spotted without her engagement ring on recently, and the reason is because of a very common symptom of pregnancy!

The Duchess of Cambridge was visiting Great Ormond Street Hospital in London recently when she was snapped without the stunning sparkler, which used to belong to Princess Diana.

Although it's not something Kate commented on during her outing to open a new building at the facility for children, we can't help but wonder whether a pregnancy symptom is behind her decision to go without.

Many mums-to-be experience a mild amount of swelling in their hands when they're expecting. Oedema occurs as a result of women's bodies retaining more fluid than usual when they're pregnant.

Kate - who looked effortlessly elegant in a bright red coat from high street store Boden - graciously thanked the hospital for inviting her along for the special occasion.

'I'd like to thank you for having me here today', she said. 'It's been my first visit to great Ormond Street and I've been so impressed by everything I've seen and the scale of the work going on here.

'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.'

Prince William's wife went on to praise staff for managing to create such a wonderful atmosphere at the hospital.

'My main message is congratulations to you all. It means so much to the families, both to the parents and children. You can see the real family element the hospital brings at such a difficult time', she continued.

'So well done, huge congratulations and I wish you all the very best of success in the future.'

Kate, 36, and her 35-year-old husband's first child Prince George was born in 2013 and a little girl named Charlotte followed in 2015.

The duo are set to welcome their third child in April this year.