STEVE INSKEEP, HOST:
There are more than a dozen medically approved methods of birth control - condoms, the pill, implants and now your phone. For the first time, an app has been certified as a method of birth control in the European Union. One of the creators is a particle physicist from Switzerland. Lauren Silverman reports from our member station KERA.
LAUREN SILVERMAN, BYLINE: Elina Berglund isn't just any physicist. She was on the team that won a Nobel Prize in Physics in 2013. Not long after, she left her friends at the lab in Geneva and set out to work on an app to prevent pregnancy.
ELINA BERGLUND: I basically locked myself in our apartment for one year to finalize the algorithm and the app. So I think I went a little bit crazy that year not having any colleagues to talk to.
SILVERMAN: Berglund had used a hormonal birth control implant for a decade, but she and her husband were thinking about having a kid soon and in search of a natural way to avoid pregnancy in the meantime. None of the existing apps met their standards, so the pair used math to create one. She says programming the app wasn't that different from what she worked on in particle physics.
BERGLUND: Instead of looking for the Higgs particle, you look at women's temperatures and fertility data, which is also a lot of fun so...
SILVERMAN: Berglund and her husband launched Natural Cycles in Sweden in 2014. They've since put up videos to educate users.
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UNIDENTIFIED WOMAN: It's important to measure your basal body temperature first thing in the morning.
SILVERMAN: Women have to take their temperature first thing in the morning and record details about their period. The app uses that information to track fertility. On days when the risk of pregnancy is high, a red light indicates avoiding intercourse or using protection. A green light is for go.
PAULA CASTANO: Women have been tracking their periods forever. We've just had to use initially paper calendars, and then we could use the calendars on our phones. And then ultimately now, we've actually got specific apps that can help us do that.
SILVERMAN: Dr. Paula Castano is an OB-GYN at Columbia University. She says, in general, menstrual cycle tracking apps are very popular. There are more than a thousand to choose from. Women download them for different reasons.
CASTANO: It could be you just want to know when is my next period going to come, and is that going to coincide with my vacation? Or can I use it to help me either avoid pregnancy or plan for a pregnancy?
SILVERMAN: The Natural Cycles app stands out because it's the world's first to get approval by a European health agency as a contraceptive. In a study of 4,000 women who used the app, along with a very sensitive thermometer, 7 out of 100 had unintended pregnancies. That might sound high, but with traditional fertility-based awareness methods - think the calendar method - 24 out of 100 women have unintended pregnancies. So how does the app compare to other forms of birth control, like the pill? Dr. Ellen Wilson, an OB-GYN at UT Southwestern, says...
ELLEN WILSON: You could argue that the app may be comparable to someone who may not be taking the pill very consistently or accurately. But if you take the pill on a regular basis and don't miss any, I don't think that you're going to have a natural family-planning method that is going to compare.
SILVERMAN: The effectiveness rate of long-acting birth control, like a hormonal IUD, is nearly 100 percent - much higher than a fertility-based awareness method or the Natural Cycles app. But, Dr. Castano points out, some women want a natural alternative.
CASTANO: So it's great for them to have something that they can use that's based on some sound medical evidence. Very few apps even have that.
SILVERMAN: Natural Cycles costs about $10 per month and has 300,000 users. Most are in Northern Europe, but Berglund has her eyes on the U.S. She says the goal isn't to replace other forms of birth control, it's to provide a more accurate mathematical update to an ancient option. Lauren Silverman, NPR News.
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