Peaches Geldof said she never planned the "crazy synchronicity" that saw her son born on her late mother's birthday on April 24.
The star, who said she was upholding "family tradition" by being criticised over her choice of name for her baby son Phaedra, insisted she was amazed to be told he would share the same birthday as her late mother Paula Yates.
She told Hello! Magazine: "It wasn't an option. Maybe it is if you go private, but we didn't and were given the date randomly by a consultant. I was pretty amazed when I read it though, and had to smile. I couldn't help feeling Mum must have had a hand in it."
The 24-year-old wed musician Tom Cohen, 22, father of Phaedra and his big brother, 13-month-old Astala, in the grounds of her father Sir Bob Geldof's country home in Kent last summer.
Astala had also originally been due on April 24, but his birth was brought forward so Peaches could have a caesarean.
She said: "It's like Mum was very determined that one of her grandsons would be born on her birthday. There's this kind of crazy synchronicity to it."
Revealing the new arrival's full name to be Phaedra Bloom Forever, she joked: "I wouldn't be a Geldof if I didn't get stick in the press about my ridiculous choice of names. I've got to uphold the family tradition.
"We chose Bloom because my middle name is Honeyblossom and also in homage to Nirvana's In Bloom. 'Forever' we chose purely because it sounds cool. I love his name and think he sounds like a rock star.
"We liked Phaedra because it features in a song both Tom and I love by Lee Hazlewood, called Some Velvet Morning. It's nothing to do with some band called Tangerine Dream, as has been reported. I've never heard them."