The Duchess of Sussex told friends she felt like ''a balloon'' when she went overdue with her pregnancy.

The 39-year-old former actress found her engagement ring no longer fit and couldn't resist poking fun at her increasingly-growing shape after going beyond her April due date with her son Archie, who was eventually born on 7 May.

According to new biography 'Finding Freedom', Meghan ''jokingly called herself 'a balloon' to a friend as her due date of April 28 came and went.''

But even after going beyond her due date, the duchess - who married Prince Harry in May 2018 - carried on staying as active as possible.

The book explained: ''As her pregnancy went into the first week of May, she stuck with the modified yoga routine she had done every morning throughout.

''She also made long walks with their two dogs part of her daily ritual upon moving to Frogmore.''

And while a friend said Meghan felt the period she was overdue was the ''longest eight days of her life'', she managed to stay calm.

The source added: ''But her patience and calm were amazing during that time - she just said 'The baby will come when it comes' and that was that.''

Archie was born in an ''uncomplicated birth'' at 5.26am on 7 May, and the family returned to their Frogmore Cottage home just a few hours later.

Authors Omid Scobie and Carolyn Durand wrote: ''It was soon after Archie was born, but Dr Penny had given the all clear and Meghan felt up to getting back home, where she could continue to be monitored.

''Although Meghan spent just a short time in the hospital after Archie's birth, when she texted friends with the news back home while the baby slept, she described being elated, if tired and a little overwhelmed.''