If you rely on a fertility app to track your cycle, bad news: Most of them miscalculate the fertile window, according to a recent study.
The study included the top 20 fertility websites found using a Google search, and the 33 most popular fertility apps in the Google Play store and the Apple App Store.
Usually, a woman with a standard 28-day menstrual cycle will ovulate around day 15, which would also be the last day of a six-day fertile window. While most reliably predicted the day of ovulation, the research found that only four provided the correct fertile window.
This suggests thousands of women are being wrongly informed about when they are most likely to conceive.
Dr Robert Setton, a researcher at Weill Cornell Medicine and New York Presbyterian Hospital, said that before using any website or app, women need to understand that the actual fertile window consists of the day of ovulation plus the preceding five cycle days.
The findings suggest that women should be cautious about relying only on websites and apps to predict the best days each month to try to conceive, the authors concluded. The study appears in Obstetrics and Gynecology.