When the US Supreme Court struck down the constitutional right to end a pregnancy last week, one step many Americans took was to delete an app off their phone: their period trackers.
There are hundreds of apps on the market that help users monitor their menstrual cycles, whether they are trying to conceive or avoid pregnancy altogether.
The two most popular apps in the US, Flo and Clue, are estimated to be used by 55 million Americans each month.
But when the landmark ruling that has protected abortion access, Roe v Wade, was toppled late last week, activists immediately warned of a possible future of digital surveillance.
From period tracker apps, to online search histories and text messages, pro-abortion groups say it could all be used as evidence in a hypothetical criminal case.
How could this data put people at risk post-Roe?
Trigger bans began snapping into place immediately after Roe v Wade was overturned, with some states banning abortion from six weeks, or even from the moment of conception.
The laws vary, and while most, so far, limit penalties to those who carry out or facilitate terminations, advocates fear that politically motivated prosecutors could attempt to have things interpreted differently.
Analysis from the Center for American Progress — published the day before the Supreme Court decision — identified nine states where abortion legislation does not protect people seeking abortions themselves from prosecution.
The fear is that any information online that indicates someone may be seeking out an abortion could be used against them.
It's a scenario that has already played out to some degree. Mississippi woman Latice Fisher was charged with second-degree murder in 2017 after prosecutors used her search history and online purchasing information as evidence that she had sought out an abortion.
Ms Fisher pleaded not guilty and said while she had researched her options early in her pregnancy, she experienced a stillbirth.
A grand jury declined to recommend she be prosecuted after an autopsy concluded there was "no identifiable evidence of external or internal traumatic injury" to the stillborn baby.
It was these types of cases that had abortion advocates urging people to delete their apps as soon as Roe was overturned.
Period tracker and fertility apps typically invite users to share a wealth of personal health information and potentially sensitive data — frequency and severity of symptoms throughout the cycle, sexual activity, use of birth control, and the start and end dates of periods and pregnancies.
Given the complexities of data security and privacy, there is a growing concern that this information could easily be passed on to authorities in states cracking down on abortions.
"The concern is about how data from these period-tracking apps might be used to show that someone might have had an abortion or was thinking about getting an abortion," Swinburne University law school's Georgina Dimopoulos, a privacy expert and law lecturer, said.
"[It's] about the data you input into these apps. Where is it going? Who's using it? And how might it be handled in a criminal case in states that might proceed to legally ban abortions?
"At the moment, there's no precedent for how that data might be used in a criminal case. There is scope for it to possibly be used in this context and so that's why there's concern amongst privacy experts that using these period-tracking apps are a form of surveillance."
Period tracker app companies say the data is safe
App developers were quick to react to concerns about the safety of the information they gather from users.
Clue said it had been inundated with questions from its customers.
"We completely understand this anxiety, and we want to reassure you that any health data you track in Clue about pregnancy or abortion is private and safe," the company tweeted.
While its terms and conditions say it complies with legal subpoenas that are issued in "good faith", the company suggested it would not honour any demands for information about Americans who may have sought an abortion.
It also pointed out that, as a company based in Germany, it is under European Union restrictions.
"EU privacy regulation is the strictest in the world. That means we are not allowed to disclose our users' private data, regardless of where they live. And, most importantly, we would never do it," the company said.
Another app, Flo, says it will soon launch an anonymous mode that would give users the option to remove information from their accounts.
It may be hard for the company to reassure some customers though.
Earlier this year, the US Federal Trades Commission filed a complaint against Flo for passing on intimate details about its users to Facebook and Google.
Flo denies that it passed on the data for advertising purposes.
Natural Cycles, the first fertility app cleared by the US Food and Drug Administration to market itself as a form of birth control, says it's scrambling to develop a "completely anonymous experience for our users".
"Our users have different beliefs, stories, goals and journeys," the company said.
Given one Supreme Court Justice has already set his sights on revisiting legislation around contraception, developers of birth-control apps will be watching closely.
Digital surveillance will weigh heavily on abortion access going forward
One way these apps have suggested users can protect themselves and their data is by bolstering their digital security defences.
Clue recommended adding layers of security for access to the app and enabling data remote erasure in case of a lost or stolen phone.
However, the concerns are far more wide-reaching than menstrual-tracking apps.
"I think this Supreme Court decision — which clearly is a fundamental violation of women's 'decisional' privacy in the US — and the flow-on effects that it has for their informational privacy, in terms of period-tracking apps … should really encourage us to think about how we understand privacy," Dr Dimopoulos said.
Amid the uncertainty over how future legislation might impact rights in this area, Americans are being urged to be more strategic about their online searches, and to use virtual private networks where possible.
"I think your instinct would be to go to Google and be like, 'Am I pregnant?' [if you've] missed a period," Flinders University's senior lecturer in US History, Prudence Flowers, said.
"We have all done our own searches like that. And Google will have that information and that kind of thing can be used against people."
And it's not just people seeking abortions who are being urged to be more careful online.
Since Friday, social media has lit up with offers of help from people in states where abortion remains unrestricted, many openly declaring, "I will aid and abet abortion", while others use coded messages to reach out.
"I live in Illinois, a state where the right to go camping is actually a law," one Twitter user posted.
"I have a spare tent & can provide transportation to a campsite."
Privacy advocates warn that this kind of information could be used against people under so-called abortion "bounty hunter" laws.
First established in Texas, and subsequently pursued by Michigan and Idaho, these laws allow private citizens to sue anyone who helps another person access an abortion.
Anyone from the doctor who performs the procedure to the driver who takes the patient to the clinic can be sued.
In Texas, for instance, a plaintiff who brings the case is rewarded with $US10,000 and their legal fees are covered by the state.
"I think people have been making claims on social media about like ... they'll host people in their homes," Dr Flowers says.
"People need to be much more circumspect in terms of what information they put out on social media about what they're willing to do for people who need abortion care."
