Sometimes even modern pregnancy tests can get it wrong, giving false negative or positive results.
Kate Moser is one of the many women who suffer depression and anxiety while pregnant.
One minute they're contentedly snuggled in the sanctuary of their mum's tummy, and the next they arrive into an overwhelming reality of lights, cameras and action.
Since the dawn of civilisation, generation after generation of new parents have had to rely on instinct, trial and error - and sometimes get it wrong.
You're out shopping with your little one and they're incessantly whining that they want a treat. It's easy to say no ... the first time, at least.
Get your free ticket to the Sydney Essential Baby & Toddler Show for September 25-27 - register online now.