In an air-starved meeting room in Manhattan’s Financial District, heavily pregnant particle physicist Elina Berglund, 35, is explaining how she inadvertently went from the cutting edge of scientific discovery to the frontline of birth control.
In spring 2012, the Swedish scientist was working in Geneva at Cern, where she was part of the team looking for the Higgs boson particle (the finding would later win the Nobel prize). It was then that she started looking for a natural alternative to hormonal contraceptives.
Pointing to the three little scars on her upper arm from where her implant sat for 10 years, Berglund remembers not wanting to get another one. “I was thinking: ‘OK, I want to have kids in a few years, so what can I do to bridge this gap?’ I felt like maybe it was a good time to let my body get back to ovulating again and get back to normal before I wanted to get pregnant.”
To bypass the implant while still controlling her fertility, she built an algorithm which analysed her lowest resting temperature each day to determine whether or not she could become pregnant (women’s basal body temperature rises after ovulation). Soon, her colleagues wanted to try it.
While on their honeymoon, her husband, Raoul Scherwitzl, who is also a physicist, suggested turning the algorithm into an app. She quickly saw the appeal: “I could see that so many women would benefit from it.” Today their app, Natural Cycles, has more than a million registered users worldwide, $37.5m in investment and 95 employees globally. It’s the first app to be certified as a contraceptive in Europe and cleared by the FDA to be marketed as birth control in the US, where it officially launched this March for $9.99 a month.
At nine months pregnant with her second child, Berglund says the app has worked successfully for her as both a contraceptive and in conceiving. “I’m a person who really likes to plan and optimise. I like to say exactly what month I want to get pregnant.”

As a contraceptive, the app claims to be 93% effective with “typical use” and 98% effective with “perfect use”. This compares with 85% typical and 98% perfect for condoms, or 91% typical and 99% perfect for the pill, according to Planned Parenthood figures.
But last year, Natural Cycles’ effectiveness came under public scrutiny.
In January 2018, the Swedish Medical Products Agency (MPA) ran a widely publicised investigation after Södersjukhuset hospital in Stockholm reported that 37 Natural Cycles users had abortions in a four-month period. The MPA later confirmed that the pregnancies were in fact in line with the product’s failure rate, but asked the company to “clarify the risk of unwanted pregnancies” in the instructions and app.
In retrospect, Berglund says it is “not so strange that they raised this alarm because it was 37 pregnancies out of 668 and of course if there’s a new product … However, what was a little bit strange was that they also went out with a press release about it.” She says she also found their decision to include typical use failures unusual.
In August, the Advertising Standards Authority in Britain ruled that a 2017 Facebook ad for Natural Cycles that included the phrases “highly accurate” and “clinically tested” was misleading. This, Berglund admits, was a mistake: “It makes no sense to talk about accuracy when it comes to contraception, you talk about effectiveness, so I think they’re completely right about that.”
When I ask about how she handles unwanted pregnancies of users personally, she seems genuinely stricken. “This is really the downside of working with contraception, that it will never succeed to 100%, so there will always be these failure rates. And these 37 women is not the first time I’ve dealt with unwanted pregnancy from Natural Cycles. We try to follow up with our users on a monthly basis and I …” she takes a deep breath in.
Through an exhale, she continues: “It’s always very hard. You want to do something good and then you have a woman contacting you because it failed for her, it’s super tough.”
Users are encouraged to check their temperature at least five days a week as soon as they wake up and enter their information into the app to find out whether they’re on a “green” (not fertile) or “red” (fertile) day. It also has “plan a pregnancy” mode.
The most common reason for unwanted pregnancies, Berglund says, is people not using protection on red days. If people used it perfectly and only on green days, she says the failure rate would be 0.5% (the 98% “perfect use” effectiveness rate takes into account condom failure). The reason it is not 100% effective, she explains, is because sometimes the body suddenly ovulates early, or there is a temperature rise that looks like ovulation but isn’t.
“My dream is if we could have a chip in the body that measures all hormones directly,” she says, somewhat optimistically. While it is almost possible on an academic level, she explains, it’s by no means imminent from a consumer perspective.
For now, though, her focus is on the US, where she says they plan to learn from their experiences in Europe. Berglund and her husband relocated from Stockholm to New York in September. So far, the response has been positive – from both the medical community and users. But of course, the birth control arena in the US comes with its own unique politics.
Women’s healthcare in America is a key political battleground for the Trump administration. It recently announced it will stop organisations that refer people for abortions from receiving government funding and has attempted to restrict access to contraception.
“As a European scientist I’m of course more pro giving the women as much option as possible and letting them choose. I think that’s more the right thing to do,” says Berglund, who describes herself as pro-choice.
But with Natural Cycles already working with Title X – a government scheme that funds reproductive healthcare to low-income Americans – to give free access to underprivileged women in New Hampshire, it seems that whether or not Berglund intends to, getting caught up in politics may be unavoidable.
How would she feel if her app was used by the Trump administration to disempower women by restricting access to other birth control methods? “Well, I haven’t seen that happening yet. If it would I would of course fight that. But not yet.” The company does not, she says, share personal data.
Berglund says many pharmaceutical companies are cutting funding for women’s health. She hopes that the booming femtech industry (predicted to be valued at $50bn by 2025) will be able to step in to fill it with more products by and for women.
And what about birth control solutions for men? Berglund plans to stick to women’s health for now, but hopes to see more male options in the future. Men, she says, have been resistant to putting up with the kinds of side-effects that women experience from hormonal contraception in studies, which doesn’t encourage research.
“I think that’s very sad because, you know … why do we have to deal with it?”
Having worked in two typically male-dominated industries, physics and tech, Berglund says she has been lucky to work among women (Natural Cycles’ staff is 65% female and 35% male.) She believes making those subjects more appealing to women in some circumstances could be as simple as reframing it. Women, she says, are often more interested in programming as a means to an end, whereas men are more often interested in the technology itself.
Her daughter Alba, who is four, is already showing an interest in nature and the universe. When she is five, Berglund says she might start teaching her about coding.