The Duchess of Sussex has marked her daughter Lilibet's fourth birthday by posting a previously unseen video on Instagram showing her dancing with Prince Harry to encourage labour in 2021.

The 43-year-old shared the intimate footage, which captures the couple performing to The Drake Family's version of Starrkeisha's "The Baby Momma Dance" shortly before she gave birth.

"Both of our children were a week past their due dates… so when spicy food, all that walking, and acupuncture didn't work — there was only one left thing to do!" Markle wrote alongside the clip.

The video shows Markle playfully twerking whilst dancing with her husband in what appears to be a lighthearted attempt to induce labour.

Prince Harry detailed the birth experience in his memoir "Spare", describing how it felt easier the second time round compared to their son Archie's delivery in England six years ago.

He recalled their bodyguards bringing "burgers and fries from In-N-Out" and "fajitas from a local Mexican restaurant for Meg" to the California hospital.

"We ate and ate and then did the Baby Mama dance around the hospital room," he wrote. "Nothing but joy and love in that room."