Kate Middleton and Prince William, the parents of Prince George, Princess Charlotte and Prince Louis, may welcome their baby no. 4 next year. The Duchess of Cambridge could share the details of her fourth pregnancy before the New Year, according to an expert.

When the classic guidelines followed by Kate in spacing her pregnancies are closely analyzed, she is likely to announce her next pregnancy by the end of this year if she is planning to have another child, said Katharine Graves, author of The Hypnobirthing Book.

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Kate gave birth to Prince George in July 2013. Nearly two years later, the Duke and Duchess of Cambridge welcomed their second child, Princess Charlotte. She was born in May 2015. The royal couple welcomed their third child, Prince Louis, in April 2018.

Kate Middleton engagement ring
Kate Middleton engagement ring Twitter

"The Duchess of Cambridge has timed her pregnancies with classic spaces. Two years between George and Charlotte and three years between Charlotte and Louis. On that basis, we could expect a fourth little Cambridge to be on the way fairly soon," Graves told The Daily Express.

The author further explained why Kate and William could decide to have another child by 2020. According to her, the royal children "live in a goldfish bowl". So, it is always "healthy to have siblings to grow up with".

Rumors about Kate's fourth pregnancy have been doing the rounds for several months. Her absence from the official tour of the Middle East with Prince William and her absence from the Tusk Conservation prompted royal fans to speculate about her pregnancy.

When the Duchess was carrying Prince George, she cancelled her official tour. During the past three pregnancies, she used to cancel most of her royal engagements due to a condition called hyperemesis gravidarum.