Fertility Tracking Apps: Are They Accurate?

Fertility and period-tracking mobile apps and websites may be inaccurate, a new study found.

These apps and websites are increasingly becoming popular among women who are trying to get pregnant as they help women track their ovulation. But a recent study reveals the fertility windows predicted by these apps and websites are inaccurate.

"Websites and electronic apps used by the general public to predict fertile windows are generally inaccurate," Dr. Robert Setton from the department of obstetrics and gynecology at Weill Cornell Medical College, said in a report published in Live Science.

Researchers analyzed 53 popular websites and smartphone apps that predict a woman's fertile window or the days when she can become pregnant during a menstrual cycle.

In the "gold standard" medical method of determining fertility, a woman's most fertile days are her ovulation date and the five days preceding that. To test the accuracy of the apps, the researchers entered a hypothetical cycle of 28 days with four days of menstruation in each of the apps. They set the last menstrual period to January 1, which means the date of ovulation is January 15 and the fertile window was January 10 to 15. Researchers marked the app accurate if the app's fertile window matched with their calculations.

Some of the apps did not specify a single day of ovulation, but there were others that predicted the date accurately. Eight out of 10 websites that gave the right ovulation date, which is January 15, and 20 out of 23 apps were also correct in giving the date. All of the websites and apps also predicted correctly at least one of the days that were within the gold standard fertility window.

However, the fertility windows predicted by these apps and websites still varied widely. One app predicted a 12-day fertility window, while others have four days. Also, about 75 percent of the websites and apps have days after the ovulation date in the window.

"None of them really tell you how they are coming up with this. There doesn't seem to by any rhyme or reason," Setton said in an interview with Time.

Although the difference may be a few days only, Setton said that suggesting a fertility window that is a few days early or a few days late "may lead to patients having intercourse in patterns that will not maximize their chances of conceiving."

While most apps did not get the fertile window correctly, the researchers cannot say that these apps are not entirely helpful in getting pregnant.

"Anyone that's trying to get pregnant should be in consultation with their OBGYN to talk about ways to maximize their chances," Setton said.

The study was published in the journal Obstetrics & Gynecology.