The Ovia pregnancy-tracking app. (Philip Cheung for The Washington Post)

When Heather Irvine used the Ovia apps to track her trying-to-conceive months and first pregnancy, she logged pretty much everything going on with her body, from the look of her cervical fluid to the days she was having sex. But after she gave birth, the app wouldn’t let her record it without entering her newborn’s name and birthday.

So she just … didn’t.

The app ended up thinking “I was pregnant for well over two years,” said Irvine, a 31-year-old journalist in Pennsylvania. “With me, I get it. I gave my personal information. That’s what I’d agreed to. But my kid? That’s none of your business.”

After we wrote about how some period- and pregnancy-tracking apps share data with women’s bosses and insurance companies, we asked women how they felt about the surprising ways their intimate health information was being captured, saved and shared.

We received more than 100 responses from women who had used one of 30 different tracker apps — or, in many cases, two or three at a time — and who often said they felt trapped by an unfair choice: They cared about privacy, but they also found the digital trackers too valuable to give up.

To deal with that dilemma, many women said they devised strategies to compel the apps to give them what they want while also keeping all of their most sensitive data to themselves. They used fake names, logged only scattered details and even fudged data to keep the tech companies and other potential snoops off their trail.

Their stories highlighted one of the more nuanced ways people think about privacy in the modern Internet age. Many people are cautious about being exposed, misused or exploited — but they also love these apps for a reason, and they’re happy to fuzz the numbers until they feel they’re no longer at risk.

Those experiences show people are getting wise to the tech world’s insatiable appetite for personal information, said Cooper Quintin, a senior staff technologist at the Electronic Frontier Foundation who has researched pregnancy-tracking apps.

“People are becoming more aware of the surveillance-capitalism business model, and becoming more aware of the massive amounts of data being taken by these companies … and they’re taking steps to minimize that wherever possible,” Quintin said. “Companies are finally realizing that their customers want their privacy taken seriously.”

Ovia declined to comment, but representatives at competing apps said the women who used them most often shared accurate information about themselves because they wanted the best results. Glow, a popular fertility-tracking app with more than 15 million users, said it doesn’t require women to give their legal names but does ask for an email address. It also attempts to figure out which pieces of submitted health information might be made up so it can treat any outlier data “as exactly that — noise,” a Glow spokeswoman said.

“The key issue is motivation," said Virginia Vitzthum, the director of science research at the period-tracking app Clue. “People who track their cycles (whether using paper calendars or apps) are typically highly motivated to input correct data because they want to know more about themselves.”

Some women told The Washington Post that the period- and pregnancy-tracking apps’ personal benefits — helping them chart their health, understand their bodies and battle insecurities during one of the most confusing times of their lives — outweighed their potential worries of how the depersonalized, aggregated data would be used.

Some said they had shared the tracked menstrual data with their doctors and spouses, and that they gave the apps a remarkable level of trust. One woman who doesn’t want to get pregnant said she had stopped taking birth control pills because she believed so completely in the advice of her ovulation-tracking app.

(You shouldn’t do this, by the way. Only one app has been approved by the Food and Drug Administration to call itself a method of contraception: Natural Cycles, which uses a woman’s body temperature and other information to suggest the days when she most likely won’t get pregnant. It’s about 93 percent effective for the average woman, clinical studies have shown — meaning seven women out of 100 who use it will still likely conceive within a year.)

Other respondents, however, said they didn’t feel the apps were worth the mental strain. “My body is the core of my privacy, and a lot of tracking didn’t seem to help me medically,” one woman wrote. It “just led to micromanaging my body and habits, which led to stress.”

Women who did use the apps found ways to obscure their identity, using a system of aliases and throwaway email addresses or only recording scraps of information without giving away the full picture of their health.

One woman who said she had miscarried while tracking her pregnancy said she stopped using the app, and started using another, for fear the information could be misused by health-care providers to prioritize other patients. She said she also hated being reminded of her loss.

Respondents were especially resistant to the apps’ requests for early health data on their children, which several of the apps have advertised will help parents chart and assess their newborns’ growth. Some said they felt the data collection was a way of infringing on their children’s privacy before they could understand or consent. “I want them to have autonomy with their digital footprint as much as possible,” one woman wrote.

Some respondents said their worries about tracking felt painfully acute: One woman living in the Bible Belt, and another in Brazil, said they worried that their information could be exploited by government authorities or end up falling into the wrong hands.

But others said the apps were easily gamed, especially in scenarios, like Ovia’s, where employers will pay small financial rewards to encourage women to track themselves.

“My workplace uses fitness tracking with incentives, and myself along with everyone I know who uses it just lies and makes things up to get the points,” one woman wrote. “I don’t really think any of this information is any of my employer’s business. If my employer was offering money for pregnancy tracking, I would probably do the same thing I already do with the fitness tracking and just input false content.”

Many of the women said they were realistic about the nature of the Web, and they’ve long since resigned themselves to the fact that they’re tracked and targeted online. But their health information felt even more important — and worth adopting unconventional measures to protect.

“This is beyond shopping habits and purchase points,” one woman wrote. “This is someone’s life.”