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Limitations of Apps & Websites When Predicting Fertile Window

Posted by Dr Fertility on

clue-app-period-trackerA new study reveals that websites and apps that predict women’s most fertile days can often be inaccurate. The research, which tested 53 fertility calculators, found that only 4 predicted the woman’s precise fertile window. Dr. Robert Setton, the lead researcher and obstetrics and gynecology resident at New York-Presbyterian Hospital explained, “I'd recommend that consumers be cautious, and not completely rely on these sites and apps".

Ovulation calculators work by entering your last menstrual period and your average cycle length to predict when you will ovulate. For a woman with a regular 28 day cycle the app would identify the typical fertile window of day 10 – 15. This includes 5 days before ovulation and the day of ovulation.


From the 20 websites and 33 apps assessed only one website and three apps identified that fertile window. They included the site and the apps Clue; My Days - Period & Ovulation; and Period Tracker. Clue uses an algorithm to calculate and predict your own unique cycle, which means it gets more accurate the more you use it. 


Although Dr. Jennifer Wu, an obstetrician-gynecologist at Lenox Hill Hospital in New York City, wasn’t part of the study, she agreed "Many patients use fertility apps on their smartphones. They do need to be aware that many of these apps are inaccurate".


She noted that this study used an average menstrual cycle length of 28 days. "But it's actually normal for cycle length to vary from 21 to 35 days," she said.


Wu recommended the use of ovulation prediction kits to help identify the fertile window more accurately. Ovulation tests measure the level of LH (Lutenzig Hormone) in a woman’s urine to identify the surge which happens during ovulation. The websites and apps can give a good indication of when to start testing and then the ovulation tests pin point the actual days.


Source: Robert Setton, M.D., obstetrics and gynecology resident, New York-Presbyterian Hospital/Weill Cornell Medical College, New York City; Jennifer Wu, M.D., obstetrician-gynecologist, Lenox Hill Hospital, New York City; May 15, 2016, presentation American College of Obstetricians and Gynecologists annual meeting, Washington, D.C.

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