27-year-old Jayde Lawrence thought she was suffering from a burst appendix on Monday after she began feeling sharp pains in her stomach.
Her and partner Kurt Stuart rushed to a Perth hospital where doctors informed Jayde she was pregnant with her second child, Nine News reported.
Despite previously taking two pregnancy tests that returned negative months earlier, Ms Lawrence showed no pregnancy symptoms.
The couple said learning of the child was hard to comprehend, but they are now 'over the moon'.
She told Nine News, 'I was crying to him [Partner Kurt] saying there's something seriously wrong with me and he goes, 'your stomach is really swollen, I think you might have a burst appendix, you need to go to the hospital now'.'
'It's hard to process something when you have 15 minutes to go from being a normal person to laying in a bed being told you're about to give birth to a small human you had no idea you created.'
The couple already share a four-year-old daughter.