If you're hoping to become pregnant, or avoid pregnancy, there's an app for that. Apps for mobile devices are being used more often for family planning; what hasn't been clear is whether they're effective.

“A woman should be able to choose her app based on solid evidence about how well the method works and what’s involved in using it,” Victoria Jennings, lead author of a new study looking at the effectiveness of one such app, called Dynamic Optimal Timing or Dot, told TheDoctor.

When used correctly, the failure rate for Dot was one percent.

The goal was to compare the effectiveness of Dot to that of other family planning methods, using the same guidelines. The app turned out to be as effective as other contraceptive methods, the team found.

There are more than 100 fertility-tracking apps available in the App Store. Some are designed only to help women learn a little more about their cycles, but some people use them for pregnancy prevention. When women first download Dot, they can choose how they want to use it: to prevent pregnancy, achieve pregnancy or just track their cycle.

Nearly 720 women were enrolled in the study. A research software program was applied to the existing Dot app. It added pop-up reminders, surveys and enabled instant messages for participants. It also allowed all the data collected in the study to be sent directly to the research team

Women in the study were followed for up to 13 menstrual cycles. Once they entered the start date of their menstrual period into the app, it calculated their fertile window. Using the first start date entered, Dot identified the 16 days in that cycle when the woman would be expected to be most fertile. As additional start dates for other cycles were entered, the app “learned ” more about a woman’s fertility cycle and narrowed down her monthly fertile window to between 11 and 13 days. Participants also entered daily sexual history data.

Dot sent the women reminders at the beginning and end of their fertile windows, and notified them of upcoming changes in their fertility status. Dot also reminded them to avoid intercourse or have their partner use a condom on days they were most likely to conceive.

When used correctly, the failure rate for Dot was one percent, and the failure rate for ‘typical’ use was five percent, making the effectiveness of the app comparable to that of other family planning methods, such as the pill, vaginal ring and other fertility awareness-based methods.

“We found no significant difference in women’s ability to use Dot and for Dot to work well for them,” said Jennings, the director of the Institute for Reproductive Health at Georgetown University Medical Center. Women need to consider how Dot can fit into their lives, including how their partner might feel about a method like Dot.

Jennings and her team recruited a diverse population for their study, so they could see how well Dot worked for different kinds of people. The app's ease of use left the researchers confident it could be used in different settings. The researchers plan to continue to analyze the rest of the data they collected, including, Jennings said, “…types of people who use it, how they use it, and how well it works for them.”

The study was published in The European Journal of Contraception and Reproductive Health Care.