Traditional fertility predictor kits use urine to test for an increase in lutenising hormone (LH) which takes place one or two days before ovulation.
However, the new 'Maybe Baby tester' claims to measure oestrogen and salt levels found in traces of women's saliva which surges when they are most fertile, the 'Daily Mail' reported.
The manufacturer claims the 40 pound saliva test is 98 per cent accurate and could end the traditional and, less than dignified "pee-on-a-stick" method.
It uses a technology based on research from the University of Turin, Italy, the report said.
Scientists there discovered that when oestrogen is present in dried saliva, it forms a pattern resembling fern leaves - which can be clearly seen under a microscope.
With the new battery-powered saliva kit, women spit on, or lick, a tiny microscopic lens before putting the stick back in its container.
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After 10-15 minutes, the user holds the reusable device up to one eye and presses a button to activate a light.
If the lens shows pebbles and dots then the woman is not deemed to be fertile. But if small fern leaves appear on the lens, the woman is said to have two or three days until ovulation.
A full pattern of fern leaves on the lens means the woman is ovulating at that moment.
Fertility experts, however, have warned that saliva tests have a history of being unreliable.
"A study of saliva testing devices published in the Lancet found that 8/10 post-menopausal women and all 10 men tested positive for ovulation," Jane Knight, Fertility Nurse Specialist at the Zita West Clinic said.
"They concluded that the saliva test is unreliable for predicting the fertile time and its use should be discouraged," Knight said.