Kate Middleton
OK! magazine is claiming that Kate Middleton is expecting a baby girl. AFP / Getty Images

A tabloid is claiming that Kate Middleton is expecting a baby girl.

According to OK! magazine, the Duchess of Cambridge and Prince William are preparing to welcome a daughter.

"Kate and William found out they were expecting a girl during the 21-week scan, and since then, everyone's been asking what they plan to name her," an alleged palace insider said.

The publication reports that although the couple "felt they needed to either go with something very traditional, like Elizabeth or Mary, or something that had a lot of meaning to them," they will name their daughter after Prince William's late mother, Princess Diana.

"They decided then and there that no matter what anyone said, they were sticking to naming their baby girl after her late grandmother. Having a baby girl who carried her name will be a beautiful reminder of Diana every time he looks at his daughter," the source went on.

The Queen has also reportedly approved of it. "[The Queen] told [William] that while she knows she had her issues with Diana in the past, she couldn't deny that she was an amazing mother," the insider said.

The royal couple's second child is due in April. Royal biographer Andrew Morton had previously revealed that Kate and Prince William will name their second child Diana, if it is a girl.

"Close friends to William and Kate have told me that if it is a girl they want to name the baby after Diana. They discussed girls' names before George was born and now they're hoping the next one is a girl so they can carry out their wish to honour William's mother.

"They're not too thrilled at the thought it will be shortened to Princess Di. But it won't change their minds," Morton told The Sun.