Gina Neff, professor of technology and society at University of Oxford, tweeted the day after the ruling: "Right now, and I mean this instant, delete every digital trace of any menstrual tracking."

Her message has so far received more than 200,000 likes and been retweeted 54,000 times.

Period trackers are used to help women predict when their next period is likely to be, and are often used to either try to prevent pregnancy or to try to conceive.

There are fears that the apps could be used to punish those seeking a termination, if law enforcement got hold of the data.

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