Prince William and Kate Middleton
Kate Middleton's current baby bump is bigger than her previous two pregnancies. Pictured: Prince William and Middleton attend a dinner at the Royal Palace on Feb. 1, 2018 in Oslo, Norway. Getty I mages/Chris Jackson

Kate Middleton's current baby bump is bigger compared to her two previous pregnancies.

The 36-year-old royal is only a few weeks away from her due date. As the arrival of her and Prince William's third child draws near, it has been observed that Middleton's bump is a little bit bigger compared to when she was expecting Prince George and Princess Charlotte.

According to an expert, the observation is correct. Aly Dilks, clinical director at the Women's Health Clinic, explained the theory behind this and said that this was due to biology.

"Essentially, each pregnancy will have its own differences and similarities but we do expect ladies to have bigger babies the more children they have," Dilks told Daily Mail (via AOL).

"During your first pregnancy the body uses hormones to make changes to accommodate the baby," she continued.

On the second pregnancy, the body has already changed and the ribcage has widened so the baby bump is more visible at the earlier stage. By the third, the adjustment in one's physique is a lot easier.

Prince William and Middleton are set to welcome their third baby in April. However, the palace remains mum regarding the duchess' exact due date and the child's gender.

Royal fans have speculated that the Duke and Duchess of Cambridge are expecting a girl because Middleton's bump is "high and wide." Meanwhile, others are convinced that Prince George and Princess Charlotte's sibling will be a boy because the royal mom wears blue more often these days.

Ulrika Johnson, who predicted her own pregnancies accurately, also suggested that the new addition to the family is a boy. "I remember my English grandmother talking about how, when the baby is 'out front' as opposed to 'spread evenly,' it was a boy," she said.

However, an expert said that one's bump has nothing to do with the gender of the baby. "Kate Middleton's baby bump has nothing to do with the gender of her third baby with Prince William," Dr. Sherry A. Ross said. "There are no truths to any of these old wives' tales I've come across during my 25 years practicing as an ob-gyn."

According to Dr. Ross, a mother's bump has a lot to do with her size and shape. For instance, tall women are likely to have smaller baby bumps. Meanwhile, shorter women tend to have a low bump.