The Duchess of Cambridge is now eight months pregnant – meaning the arrival of a new royal baby is now pretty much imminent.

And other than the obvious excitement, Catherine’s baby bump hasn’t gone unnoticed with royal fans, with many pointing out that it looks slightly bigger than when she was pregnant with Prince George and Princess Charlotte.

Looking back at pictures of the Duchess at the eight-month milestone with her first-born in 2013, it seems the Duchess did have a slightly smaller bump than she has at the moment…

And the royal’s bump certanly looks a little smaller weeks before she welcomed Princess Charlotte in 2015 too.

So why the change in bump between her three children?

Well, according to Aly Dilks, a former midwife and Clinical Director at The Women’s Health Clinic, it’s totally normal to see a bigger bump with your third child than with your first, or even second.

Talking to the MailOnline, she explained that the rib cage has generally expanded by the time a woman has had her first child, making the baby bump appear bigger.

She said, “By the second pregnancy, the rib cage has already widened giving the uterus plenty of time to expand and baby to ‘pop’ more quickly.

She also credited the body’s sense of muscle memory for causing a slightly bigger bump.

“In subsequent pregnancies the body has a sense of muscle memory, so patients often report digging out their maternity jeans almost as soon as the test turns positive.”

Of course, during pregnancy stomach muscles also expand, which could explain Catherine’s larger bump.

The Duchess of Cambridge is due to give birth to her third baby next month – although an exact due date hasn’t yet been confirmed.

It’s thought that the Duchess has just one public engagement left before her maternity leave begin. On 22nd March, she will attend some Commonwealth events with Prince William. During one visit, the royal couple will help prepare a Commonwealth Big Lunch, at St. Luke’s Community Centre.

We can’t wait until the new royal bubba arrives!