More than 20 per cent of Australian adults never become parents, but it is impossible to distinguish which out of these group are child-free by choice or childless by circumstance.

On Tuesday evening's episode of Insight on SBS, a whole range of child-free adults shared the reasons behind their lack of offspring.

Two of the most captivating accounts were from Kate Murray, who was 'scathing' in her opinion of parents as 'selfish' people, and Mandi Whitten who never wanted children until she couldn't have them.

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On Tuesday evening SBS's Insiders spoke to Australians that are child-free by choice, pictured are Yang-En Hume (left) and her husband Geoff

'I saw breeding as a very selfish thing to do, and I saw it as something that people who didn't have anything else to do did, so it was a way of feeling like you've achieved a lot in life without doing much,' Ms Murray told the program.

The woman admitted she was 'scathing' in her opinion of parents, and took issue with the way society views motherhood.

However when she fell pregnant with her long-term partner - a 'family man' - her views about starting a family of her own were called into question.

Ms Murray said before she was presented with the real possibility of having a child, she was adamant she didn't want to give up her life, and struggled through the first stages of pregnancy.

'The first stages of pregnancy I was like oh my god, I'm infested with this alien life and it was creeping me out,' Ms Murray said.

Another audience member, Yang-En Hume, shared Ms Murray's fear of having a baby growing inside her.

Kate Murray was 'scathing' of parents calling them 'selfish', but now has a 10-month-old baby girl

'The thought of being a mother horrifies and repulse me, the thought of being pregnant fills me with disgust, I hate the idea of having a human living in my uterus, I hate the idea of birthing a human being through the natural process, I hate the idea of breastfeeding,' Ms Hume revealed.

'The entire biological process makes me feel very anxious.'

Speaking of her own experience, Ms Murray also said that the discussion around parenting was not realistic enough, and instead was sugar-coated into being always about the positives.

'I don't know why we have that rhetoric, I don't know why we don't have a more honest dialogue amongst women because.. it is messy and it is hard and it is also joyful,' Ms Murray told Insight.

Another compelling story came from Mandi Whitten, who since she was a young girl was convinced she would never have a family of her own.

Mandi Whitten was convinced she didn't want children until she had a radical hysterectomy to treat her cervix cancer and realised she no longer could

'When I was much younger I thought I wanted to have kids, and then as I became a teenager I realised that the world was a big scary horrible place and I thought actually no, I don't want to bring a child into that,' she revealed.

Ms Whitten was diagnosed with cervix cancer at the age of 35, the treatment for which was a 'radical hysterectomy'.

This is where the surgeon takes out the uterus and the ligaments that hold it in place in the pelvis. The cervix and an inch or two of the deep vagina around the cervix are also removed.

'Since then I've regretted not having children, and I still hold that regret,' Ms Whitten revealed.