Don't Count on Websites and Cell Phone Apps to Predict Fertility Accurately

Websites and cellular phone applications (apps) are increasingly popular in many contexts. Investigators evaluated the accuracy of these resources in predicting the “fertile window” during which conception is most likely. The gold standard is based on data of Wilcox et al. (N Engl J Med 1995; 333:1517) and assumes that a cycle's most fertile days are the day of ovulation and the 5 preceding days. To assess 20 fertility websites and 33 apps, the authors selected a hypothetical date of last menses and assumed that each menstrual cycle was exactly 28 days in length, then compared the assumed actual dates with predicted dates generated by these resources.

Eight websites and 20 apps correctly forecasted the date of ovulation; however, the predict…