A recent study published in Contraception revealed that the fertility app Natural Cycles is 99 percent effective when used perfectly. The app makes use of daily body temperature readings to determine when it is safe to have unprotected sex and when to use contraception or abstain from sex. Days rendered as safe for unprotected sex were classified as green days, while days that require protection or abstinence were considered red days.

In order to carry out the study, researchers examined 22,785 women and pooled data from a total of 224,563 menstrual cycles across a year in order to evaluate the app’s Pearl Index. The index was traditionally used to measure the efficacy of a given contraceptive.

The results showed that using the app perfectly, which meant using protections such as condoms during red days when pregnancy is likely to occur, was 99 percent effective in preventing unwanted pregnancy.

The study also found that typical use of the Natural Cycles app, where people use protection on red days, was 93 percent effective in inhibiting the onset of pregnancy. This was higher than other natural family planning methods that rate at around 75 percent, researchers said.

The researchers also stressed that the app was even more effective in preventing unwanted pregnancy compared with using birth control pills, which exhibited an efficacy of only 91 percent.

“What we see in our data, which I find very promising, is younger women getting pregnant less when using the app even though they are more fertile, because they really don’t want to get pregnant. Slightly older women are those that get pregnant the most using the app…People usually say what they like the most about the app is that it knows their body and helps them understand what’s going on inside…70 percent of our users come from hormonal contraception, and we see in our data that it’s very common that disrupts your cycle, sometimes for up to one year. 70 per cent of our users come from hormonal contraception, and we see in our data that it’s very common that disrupts your cycle, sometimes for up to one year,” Natural Cycles developer Elina Berglund said in a Wired article.

Natural Cycles remains to be the only app of its kind to be treated and regulated as an approved medical device. This puts the app in the same category as intrauterine devices and condoms, but in a different class.

Results remain constant for Natural Cycles app

The recent findings were consistent with a clinical trial carried out in October last year. As part of the trial, the researchers examined data on more than 4,000 women aged 20 to 35 years old.

The results showed that up to 143 unplanned pregnancies occurred over the course of one year. The trial also revealed that 10 of these pregnancies occurred during green days, which rendered the app 99.5 percent effective. The app’s efficacy rate was comparable with that of a birth control pill, researchers noted.

Critics were a bit more skeptical of the results, stating that abstinence is still better than having unprotected sex and that the app may not be fit for that purpose. However, lead author Kristina Gemzell Danielsson stressed that the app was not recommended for women who were very young or those who were really keen to prevent pregnancies.

“It is important to notice that our study was a real-life study, which means the performance of Natural Cycles was assessed as close to reality as possible. In controlled clinical trials, the performance is always better because there is a lot of supervision from clinicians that remind for example women to take the pill, to use condoms, and so on,” Berglund wrote in a separate Wired article.

Sources include:

Wired.co.uk 1

Wired.co.uk 2