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The big clue that Kate Middleton will give birth on the last weekend of April

The Duke and Duchess of Cambridge will celebrate their seven-year wedding anniversary on Sunday 29 April

Ainhoa Barcelona

There could be double celebrations this year when Prince William and Kate mark their seventh wedding anniversary. Royal watchers are speculating that Kate will give birth on the weekend of Saturday 28 and Sunday 29 April, judging by her past maternity leave plans. When Kate was pregnant with Prince George in 2013, she carried out her last official engagement on 15 June, attending the Trooping the Colour parade in London. She then began maternity leave and her son was born 38 days later on 22 July.

Similarly, when Kate was pregnant with Princess Charlotte, she made her last official appearance on 27 March 2015, visiting the Stephen Lawrence Centre in London with Prince William. The Duchess went off on maternity leave and gave birth 37 days later, on 2 May. Charlotte was due in April but kept her parents waiting for a few days.

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Kate gave birth to Prince George 38 days after Trooping the Colour in 2013

Kensington Palace have just confirmed that Thursday's engagement is Kate's last one before she goes on maternity leave. Judging by her past plans and due dates, Kate could give birth in 37 or 38 days, which means the baby would be born on Friday 27 or Saturday 28 April. William and Kate's seventh wedding anniversary falls on Sunday 29 April.

GALLERY: Absolutely everything you need to know about the royal baby

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Kate gave birth to Princess Charlotte 37 days after her final engagement in 2015

It was previously reported that Kate is due on or around 23 April, which coincidentally also marks the feast day of the patron saint of England, Saint George. If the baby is late, the birth would happen closer to William and Kate's wedding anniversary – a very special present for the couple.

It's understood that the Duke and Duchess are keeping the gender of their third child a surprise, but Kate is expected to give birth at the exclusive Lindo Wing at St Mary's Hospital in Paddington, London. The hospital has welcomed several royal babies including Prince George, Princess Charlotte, Prince William and Prince Harry.

GALLERY: Kate's sweetest photos with George and Charlotte

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