Of all the misinformation I hear from patients, this is the myth that I hear most commonly. “My app tells me when I’m ovulating”. Here’s the thing, apps that track periods are predicting the fertile window based on a math equation, not on your actual body.
Let’s review the monthly cycle. The first half of the cycle, from the first day of a period to ovulation is called the follicular phase, and the second half, from ovulation to the next period is called the luteal phase. The length of the luteal phase is pretty consistent from month to month, lasting about 12-16 days.
But the follicular phase is susceptible to change. Ovulation can be delayed by stress, travel, moving, illnesses, meds, strenuous exercise, and sudden weight changes. This is why when we might have a late period when we’re having a particularly stressful time in life. It’s because the follicular phase was longer than usual, ovulation was late, and so the period is late.