# most women have a couple of anovulatory cycles every year
> In fact, in the less than 400 women in epidemiology studied for ovulation, the information suggests that in any given regular cycle you may not ovulate once or twice out of a year’s worth of 13 cycles.[[(Prior, 2014)#^n25nv]]
> We have estimated that approximately 10-20% of women’s cycles are anovulatory and about a third have short luteal phases thus ovulatory disturbances occur in a high percentage of seemingly normal menstrual cycles. Thus we know that ovulatory disturbances with their normal estrogen but lower progesterone levels are both common and silent.[[(Prior, 2014)#^3ohvv]]
> **Conclusion:** Anovulation in a random population occurs in over a third of clinically normal menstrual cycles[[(Prior et al, 2015)#^4od32]]