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A new review of the exploding market in period-tracking apps gives the technology a failing grade.

A research team at the University of Washington examined a number of the wildly popular apps — including Clue, Eve, Glow, Period Tracker, and Pink Pad — and found many came up wanting.

Though they collectively attract millions of users, some of whom rely on them for fertility predictions, the apps are often far from accurate — especially for women whose cycles are not regular. “And those are the people who need the apps most,” said Daniel Epstein, a UW doctoral student studying human and computer interfaces who led the research.


The lack of accuracy is disturbing given that women may rely on the apps to schedule expensive infertility treatments — and that many teenagers use the apps as a primary form of birth control, counting on them to flag the days in the month when they are least likely to become pregnant, said coauthor Julie Kientz, an associate professor of human centered design and engineering at UW.

The apps are also largely one-size-fits-all. They don’t account for the way a woman’s menstrual patterns may change while pregnant, breastfeeding, or entering menopause, the researchers said.


Another problem: Many of the apps are pink and flowery, which women interviewed by the researchers said made them embarrassing to open up.

Many period-tracking icons literally do include huge, pink flowers. Others use images such as pink bikini underpants, or large pink dots on calendars. “All that pink in the interface made people feel awkward,” Epstein said. “They felt bad opening the app in public.”

Yet another flaw: The design and wording of the apps, which usually refer to the users as female and their sexual partners as male, aren’t welcoming to users who are gay — or who may menstruate but identify as male. “It makes people feel excluded by their apps,” Epstein said.

There are dozens of menstrual tracking apps available, some marketed specifically for fertility and others as birth control reminders. They range in price from free to $5.99 and analysts see them as a robust and growing sector of the health app market. Twitter traffic shows many users are thrilled with their trackers, while others are outraged by inaccuracies.

Epstein and his colleagues decided to focus on period-tracking apps because they are becoming so popular — Clue reports it has more than 5 million users worldwide — but have been little studied.

The team combed through several thousand reviews of the apps, then conducted surveys and interviews with users. They will present the paper next week at a conference on human factors in computing being held in Denver.

The team is hoping that app developers will use their results to improve their products. One simple way may be by letting users correct their apps when predictions are wrong, so the apps can learn the women’s cycles and become more accurate over time.

Another recommendation: Drop the “shrink it and pink it” mentality and use sleek, gender-neutral interfaces.

As for users of apps, the researchers offer this advice: Don’t rely on the predictions for fertility or birth control. And since many of the apps are free or low-cost, download a couple and use them in parallel for a few months to find out which one works best for you.