Researchers found most fertility apps are unlikely to help women prevent or plan a pregnancy.
Lead researcher Dr. Marguerite Duane, of Georgetown University School of Medicine in Washington, D.C., and colleagues came to their conclusion after conducting a review of almost 100 fertility apps.
According to Dr. Duane, the use of such apps is gaining popularity, as an increasing number of reproductive-age women look to use fertility awareness-based methods (FABMs) as a way of having greater control over whether or not they become pregnant.
The American Congress of Obstetricians and Gynecologists (ACOG) describe fertility awareness as "knowing and recognizing when the fertile time (when a woman can get pregnant) occurs in the menstrual cycle."
While fertility apps vary in their capabilities, they generally work by helping users to track their menstrual cycle, allowing them to pinpoint ovulation - the time at which pregnancy is most likely to occur.
Some apps also track a woman's basal body temperature (BBT) - the temperature when the body is fully at rest; according to ACOG, a rise in BBT normally occurs 2-3 days after ovulation, so it is not a good idea to use BBT by itself to avoid or achieve pregnancy.
Other apps also allow women to track their cervical mucus; the presence of such mucus normally occurs when a woman is at her most fertile.
But are fertility apps an effective way to plan or prevent pregnancy? This is what Dr. Duane and colleagues wanted to find out.
Only six fertility apps had perfect accuracy, no false-negatives
For their study - due to be published in the Journal of the American Board of Family Medicine - the researchers identified more than 95 fertility apps that are available to download through iTunes, Google, or Google Play.
The researchers found that 55 of the apps either had a disclaimer stating they were not to be used to avoid pregnancy, or they failed to use an evidence-based FABM, leading to their elimination from review.
To review the remaining 40 apps, the team applied a five-point rating system that used 10 criteria considered important for avoiding pregnancy.
The team found that 30 of the apps reviewed predicted fertile days for the user, while the remaining 10 did not.
A perfect score for accuracy or no false-negatives was only achieved by six of the apps, the researchers report.
Among apps that did not predict fertile days, a high accuracy score was only achieved if the apps required women to undergo training in an FABM before use.
Based on their findings, the researchers do not advise relying only on fertility apps to avoid or achieve pregnancy.
"The effectiveness of fertility awareness-based methods depends on women observing and recording fertility biomarkers and following evidence-based guidelines. Apps offer a convenient way to track fertility biomarkers, but only some employ evidence-based FABMs."
Dr. Marguerite Duane
For women who wish to use fertility apps, Dr. Duane offers a word of advice.
"When learning how to track your fertility signs, we recommend that women first receive instruction from a trained educator and then look for an app that scored four or more on mean accuracy and authority in our review," she says.