And because she is pregnant with her and Prince William's third child, she will be off the booze.
She might be royal but there was no VIP treatment for the Duchess of Cambridge on her big day, with Kate opting for a very low-key affair.
And the Duchess of Cambridge had more reason to celebrate today as she marked her 36th birthday at home in London.
'But she is not drinking any alcohol and she is being careful with her food too.
Meanwhile, a source revealed to Daily Star Online that Middleton has got a small birthday party of eight and that it was quite a low key party. It was said to be a "low key party" at Kensington Palace.
The Royals received a warm welcome at St Mary Magdalene church, where large crowds gathered to see them arrive for an Epiphany service.
Thier wedding is set to take place in spring on May 19, 2018.
Throwback Photos of Kate Middleton on Her 36th Birthday
To celebrate Prince William and Kate Middleton's fourth wedding anniversary here are their relationship in pictures.
The glowing Duchess, who spent her 35th birthday at Amner Hall in Norfolk, showcased her bump in a longline brown tweed coat paired with leather gloves and a furry hat.
Pippa Middleton with husband James Matthews. She's heavily pregnant with her third child, due in April, so it's no wonder she'd prefer spend a relaxing day out of the public eye.
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