With July 11 marked as the official due date for Kate Middleton and Prince William's child (and the future heir to the British monarchy), we can't help but have royal babies on the brain.

Being a member of the British royal family comes with certain responsibilities, but can you imagine being a pregnant royal? Countless public appearances and media frenzies can't make being royal mom-to-be very easy -- unless you're Kate Middleton and you always manage to look flawless, no matter what the occasion.

Starting with Queen Elizabeth II and her sister Princess Margaret, we took a look back at all the British royals who were pregnant before Kate (and one who is following in her footsteps!). From Princess Diana's sweet maternity dresses and sophisticated gowns to Fergie's bold colors and nautical-inspired ensembles, we've got all the British royal pregnancy style right here.

How does their style stack up that of the shining star of today's maternity style, Kate, the Duchess of Cambridge? Click through the gallery to see for yourself!