Dr Kerry Armstrong and Dr Simon Smith, from the Queensland University of Technology's Centre for Accident Research and Road Safety, studied 24 mothers aged 22 to 39 to investigate the impact fatigue has on new mums.
Dr Armstrong said contrary to previous research, which indicated post-partum fatigue should disappear after six weeks, new mums still felt exhausted 12 weeks after giving birth.
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The study found lifestyle changes, interrupted sleep, lack of routine and high levels of unpredictability led to fatigue, which could at times be overwhelming.
She said the mothers had reported living in a "mental haze" and "moving through the day like you're on autopilot".
"Clearly this raises concerns for driving tasks, which for an experienced driver is largely an automatic process," Dr Armstrong said.
Dr Armstrong said while most people accepted women with babies would be exhausted, up until now no one had looked at what this meant for their safety on and off the road.
"To put the danger of fatigue into some sort of perspective - if someone is awake for 17 hours they have a driving performance similar to that of a person with a blood alcohol level of 0.05 per cent," she said.
"And if they have been awake for 24 hours it is 0.1 per cent, or two times the legal driving limit.
"This has serious implications for mothers suffering from interrupted sleep patterns, night after night and sometimes for several years."
Dr Armstrong said the findings from the study would be used to develop an information booklet.
