Nicky Hilton Rothschild is "thrilled" to be pregnant with her second child

A representative for the star said: "The couple are thrilled about the new addition to their family."

It comes after a source claimed Nicky was past her second trimester and had confided about the good news with her friends at Princess Olympia and Prince Pavlos' joint birthday party over the weekend.

A source said: "It was a Marie Antoinette costume themed party so she was wearing a corset so no one could tell. It's Lily's first birthday July 8 so they are excited. They always wanted to give Lily-Grace a sibling close in age, like they both have."

Nicky is reportedly due to give birth in early 2018 and the couple would "love" to have a boy but would equally be pleased if they were to have another girl.

Meanwhile, Nicky's mother Kathy Hilton is full of praise for her daughter's parenting skills.

Speaking just a few months after Lily was born, she said: "She's unbelievable. Her computer and her phone have just been in the same place. We spent a month together out in the Hamptons and she's breastfeeding and it's a full time job - literally a full time job - so she can't go anywhere for more than an hour. I think we went out twice.

"With my babies, if I wanted to go pick them up I would just go in the room in the middle of the night, but Nicky is very much on a schedule. This is nap time, this is tummy time, so I'm just kind of like, 'Okay' ... I'll tell her certain things, but she's read up on everything."