Kate Middleton's mum guilt triggered by Charlotte's innocent question as she left for work

The Duchess of Cambridge admitted she suffers from mum guilt when she leaves Prince George, Princess Charlotte and Prince Louis behind to carry out her royal duties.

While Kate doesn't exactly have a 9-5 job, her role sees her travelling up and down the country for official visits, flying overseas for royal tours and attending a number of private meetings with charities and organisations she is patron on.

Just like other mums, the Duchess says leaving her trio at home is a "constant challenge", especially when they ask her why she's can't stay with them.

Speaking in her most candid interview yet, which she admitted she was nervous about, Kate opened up about parenting and childbirth on Giovanna Fletcher's podcast Happy Mum, Happy Baby.

She also spoke movingly about husband Prince William becoming a dad, their life as new parents behind closed doors and her own upbringing.

Asked if she feels mum guilt, she replied: "Yes absolutely - and anyone who doesn't as a mother is actually lying.

"Yep - all the time, Even this morning, coming to the nursery visit here - George and Charlotte were like 'Mummy how could you possibly not be dropping us off at school this morning?'

"It's a constant challenge - you hear it time after time from mums, even mums who aren't necessarily working and aren't pulled in the directions of having to juggle work life and family life."

She also says she sometimes feels guilty about the parenting decisions she makes.

She said: "[You're] always sort of questioning your own decisions and your own judgements and things like that, and I think that starts from the moment you have a baby."

She goes on to explain how she deals with the guilt, relaying something a "very wise man" told her.

She said: "The more people you have around your children who are safe and loving and caring, the better.

"So yeah - it was a real weight off my shoulders that actually it's not totally my responsibility to do everything, because you know we all have good days, bad days - and you can dilute that with others who aren't on that particular day struggling.

"I think it makes such a difference for your child, keeping them as constant and happy as possible."

During the interview, which was to raise awareness for her 5 Big Questions survey, Kate spoke openly and honestly about all three of her births, including the moment she and William welcomed their first child Prince George.

Asked what it was like holding her son for the first time, she replied: "Amazing, amazing. It is extraordinary as I’ve said. How can the human body do that? It is utterly extraordinary actually. And he was very sweet.

"And also sort of relieved that he was a happy, healthy boy."

She also gave a heart-warming description of William's reaction to becoming a dad.

"Seeing, you know your husband, William, and things like that. Seeing the pure joy of his face it was really special."

Speaking about the pressure of knowing the whole world was waiting for updates on her birth, Kate admitted she was "terrified".

Giovanna asked: "What was it like knowing that so many people outside, after you’ve given birth and you’re in your little cocoon with your new family, what’s it like?"

Kate replied: "Yeah, slightly terrifying, slightly terrifying, I’m not going to lie."

"I like to decompartmentalise - what’s the word – compartmentalise, yes, the whole thing.

"Everyone had been so supportive and both William and I were really conscious that this was something that everyone was excited about and you know we’re hugely grateful for the support that the public had shown us, and actually for us to be able to share that joy and appreciation with the public, I felt was really important.

"But equally it was coupled with a new-born baby, and inexperienced parents, and the uncertainty of what that held, so there were all sorts of mixed emotions."

Asked how long she had between giving birth and posing on the Lindo Wing steps, Kate said: "Oh my gosh, I can’t remember. Everything goes in a bit of a blur.

"I think, yeah I did stay in hospital overnight, I remember it was one of the hottest days and night with huge thunderstorms so I didn’t get a huge amount of sleep, but George did which was really great.

"I was keen to get home because, for me, being in hospital, I had all the memories of being in hospital because of being sick so it wasn’t a place I wanted to hang around in.

"So, I was really desperate to get home and get back to normality."

While it looked like Will's had the famous 'car seat' moment down to a fine art, Kate admitted they had no idea what they were doing.

"We were like ‘What do we do?... in a swaddle?’. ‘How’s this supposed to work?!’.

"We’d even tried to practice with a little baby, like a little doll, at home but you know it just never works out the way you planned it so it was quite hard to do that on the world’s stage, but no, he did a very good job."

Speaking about their first days at home with George, Kate said: "It wasn’t that quiet in our household!

"William was like ‘Oh my gosh is this what parenting is going to be like?’

"It took us a bit of time to get ourselves settled and going again but that’s the beauty, I suppose of having a new-born baby. You are pulled to your toughest and most unknown places that you hadn’t necessarily even thought about before."

Kate opened up about her difficult pregnancies saying she felt "utterly rotten" after suffering from hyperemesis gravidarum - extreme morning sickness - with all three children.

 "It was fine. I got very bad morning sickness, so I’m not the happiest of pregnant people.

"Lots of people have it far, far worse, but it was definitely a challenge. Not just for me but also for your loved ones around you – and I think that’s the thing - being pregnant and having a new-born baby and things like that, impacts everybody in the family.

"You know, William didn’t feel he could do much to help and it’s hard for everyone to see you suffering without actually being able to do anything about it.

"I wasn’t eating the things I should be eating – but yet, the body was still able to take all the goodness from my body and to grow new life, which I think is fascinating."

After much speculation Kate also confirmed she did hypnobirthing, saying she didn't discuss the idea with William at all.

She said: "I’m not going to say that William was standing there sort of, chanting sweet nothings at me. He definitely wasn’t! I didn’t even ask him about it, but it was just something I wanted to do for myself.

"I saw the power of it really, the meditation and the deep breathing and things like that - that they teach you in hypnobirthing - when I was really sick and actually I realised that this was something I could take control of, I suppose, during labour.

"It was hugely powerful and because it had been so bad during pregnancy, I actually really quite liked labour! Because actually it was an event that I knew there was going to be an ending to."

Kate also admitted that she would have done things in her pregnancy differently knowing what she knows now from her work with the early years sector.

She said: "I feel a huge responsibility because what I’ve learnt over the last few years is so fascinating and I definitely would have done things differently, even during my pregnancy, than I would have done now.

"Because you know - the science - and I found that fascinating to see the wellbeing of the mother – not just physically, you know there’s so much information about making sure you exercise and making sure you have a healthy diet and things like that, which yes is definitely important. But the emotional wellbeing of the mother directly impacts the baby that you’re growing.

"It’s difficult, and also with life’s challenges and everything like that, it really is hard but actually just being aware of it. I was a lot more aware of it third time round than I was the first-time round."

Kate also opened up about her own childhood and praised her parents Michael and Carole, reflecting on how it impacts her own approach to parenting.

She said: "I had a very happy childhood. It was great fun – I’m very lucky, I’ve come from a very strong family – my parents were hugely dedicated to us – my siblings. I really appreciate now as a parent how much they sacrificed for us.

"They would come to every sports match – I was very keen on sports – they came to every sports match, they’d be the ones on the side-lines shouting, and we’d always have our family holidays together.

"But I think the things that really resonate with me most are the simple things and actually I see that now with my own children, life now is so busy, so distracting and actually sometimes the simple things like watching a fire on a really rainy day provides such enjoyment.

"I remember that from my childhood – doing the simple things, going for a walk together, and that’s really what I try and do with my children as well because it totally strips away all the complications, all the pressures."