Is it possible to tell on the pill when a breakthrough ovulation may occur? Is there a certain time in which it probably would occur, similar to the window of time for a woman not on the pill? Or because the pill does not create a true cycle, would ovulation be possible at any time during the 21 days she is taking the (non-placebo) pill?

Answered by Cathy Ramey, EPM Volunteer

The pill is often used to “regulate” the menstual cycle, but that does not mean that you can reliably predict which cycles might involve breakthrough ovulation. If a person is using NFP to plot the course of their cycle, I suppose they would know approximately when they would be due to ovulate, but only some sophisticated testing like ultrasounding the follicle would give any precision as to whether or not breakthrough might/might not occur or does occur.