In an effort to prevent further birth defects caused by the Zika virus, Natural Cycles, the world's leading fertility app, is planning to donate one million free subscriptions, costing more than $25 million, to women living in Brazil.

"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," said Natural Cycles co-founder Dr Raoul Scherwitzl through e-mail. 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."

Last month, Centers for Disease Control and Prevention confirms that zika virus can cause a rare birth defect called microcephaly. Due to this, World Health Organization advised all women to delay pregnancy in region with high prevalence of zika outbreak.

The fertility app can greatly help women identify their ovulation and fertile window by tracking her period and temperature. The app is very easy to use. Women just need to take the temperature under their tongue before getting up and enter it. The app will then determine if the woman is fertile that day.

If the indicator is green, it means that the woman is not fertile in that day and will have a low risk of pregnancy, while the red indicator means the woman is fertile and therefore avoid any unprotected sex during that day.

The app can also be used to plan pregnancies.

Women living in Brazil can avail the free subscription on May 5, 2016. The free subscription would last up to six months or until the Zika outbreak is deemed to be under control.