Em Rusciano on the "terrifying" moment she discovered she was pregnant at 21.

Comedian, author and all-round excellent human being Em Rusciano has opened up about unexpectedly falling pregnant at 21, saying the discovery left her in “absolute shock.”

Sharing the excerpt from her book Try Hard with the Sydney Morning Herald, Rusciano admitted, “Peeing on the stick and seeing those two blue lines appear was terrifying.

“I sat on the toilet in our one-bedroom apartment and stared at the pregnancy test in absolute shock.

"I had genuinely expected it to be negative. I was an elite athlete and in absolutely no state to be having a child. I was still a child myself!"

Having met her partner Scott a year before, the couple had only been dating for a few months when Rusciano fell pregnant with their eldest daughter, Marchella.

And because life has a cruel sense of humour, Rusciano made the discovery on Valentine's Day.

Upon finding the test positive, Rusciano said, "My first instinct was to call Scott, but then I remembered that this wasn't just a parking fine or a fight with my best friend – this would drastically affect him too and what I needed was a reassuring pep talk, not a panicked boyfriend."

Instead, she called the person we all turn to whenever we find ourselves on a proverbial creek with no paddle: Mum.

"We both agreed it would be best not to tell my Italian Catholic father until I knew exactly what I was going to do myself," Rusciano continued.

"When Scott arrived home from work he was holding a bunch of roses (it was Valentine's Day, remember), so naturally I burst into tears."

After days of discussions and planning, Rusciano and Scott decided the best thing to do was have an abortion. Except when the time came, she couldn't go through with it.

"As I walked into the clinic for the procedure I remember feeling like I had left my body altogether – it was as though I was watching myself," she said.

"I sat down, was handed a clipboard and told to wait. For some reason, hearing my name called snapped me out of the fog I had been in and I instantly knew I didn't want to end my pregnancy.

"It was a moment of pure clarity. I have only had that happen to me two other times: when I met Scott and when I quit my breakfast radio job in Perth. I handed the clipboard back and said, 'I don't want this, I've changed my mind, I'm going to leave.'"

Fifteen years later, deciding to walk away that day has changed the comedian's life infinitely for the better.

Rusciano describes her daughter as her "right hand woman, legit legend and sensible golden child".

But how she got from the clinic to where she is now? It seems only a full read of the book will tell.

Try Hard is out now.