A fertility app is to be given free to one million Brazilian women in a bid to halt the spread of the Zika virus.
The Natural Cycles app works by identifying a woman's ovulation cycle and fertility window by tracking her period and temperature - the app then notifying users on days they are and are not fertile. A recent study found the app's prediction system to be wrong only 0.05 per cent of the time.
The one million free subscriptions - worth the equivalent of over $US25 million ($A33.54 million) - will be offered to Brazilian women via the App Store as a means of temporarily postponing pregnancy until the virus is brought under control.
Natural Cycles co-founder Dr Raoul Scherwitzl said: "Access to contraception is often limited in many of the countries hit by Zika due to moral and social reasons.
"Those do not apply to the Natural Cycles app as we do not interfere with a woman's body in any way - our app simply helps to educate women and their partner about her fertility.
"The data collected by the app to postpone pregnancies during this time can then be used to find the most fertile days in order to accelerate pregnancies once Zika is deemed to be under control."
The free subscriptions will be available for six months from May 5, or until threat from the virus is removed.
Zika virus, which is spread by mosquito bites, is known to cause birth defects in children who are conceived by mothers carrying the virus - leading the World Health Organisation (WHO) to declare a global public health emergency in 2015 after cases of the virus were found across Central and South America.
A recent medical study in Sweden involving more than 4000 women found the Natural Cycles app to be nearly as effective at preventing pregnancy as the contraceptive pill.
