Harry Judd's wife Izzy "struggles" knowing they still have "one more frozen embryo".
The McFly drummer and his musician wife - who have daughter Lola, seven, and sons Kit, five, and Lockie, almost three, together - had their first child after IVF treatment, and Izzy is unsure about having more kids in the future.
She told new! magazine: "Maybe if I had Lockie a bit sooner, but it's difficult to answer that question because I had IVF with Lola, but my boys came along naturally.
"Lola was a frozen embryo and we have one more frozen embryo, which I really struggle over.
"I think it's probably something a lot of people come up against when you've had fertility treatment because there are more in storage."
The Escala violinist admitted part of that is wondering "who that might be", especially after choosing one of the embryos for their eldest child.
She added: "I suppose you wonder who that might be. They could have chosen that one but we had Lola and you think, 'That could have been Lola'. It's an emotional process."
Izzy - who married the 'Five Colours In Her Hair' hitmaker in 2012 - pointed out that "nobody really prepares you" for being a parent, and she has had her share of interesting experiences.
She said: "My youngest, Lockie, has learnt to ride a bike far too early, which is just so frightening and he goes so fast, I just can't keep up.
"The other day, a lady was like, 'Is he yours?' and I was like, 'Yes', she said, 'I was a bit concerned how far away you were' and I was thinking, 'Yes, I know, I was too, but I was trying to chase him.' "
Meanwhile, "potty training" her youngest child has had its challenges because he's been trying to copy the family pet.
She said: "There are so many moments... I've also been potty training Lockie so he just thinks it's absolutely fine to wee anywhere outside.
"I'm also training the puppy as well, so Lockie is just copying."
