The interpretation of this data points to variation in cycles from month to month stating that fertility may vary from “cycle to cycle.” My take on this would be to realize that our women today are subjected to enormous physiologic stress which is causing the changes in the cycle length. 27-29 days are normal and outside of this some negative forces are at play on the ovulation cycle. The stresses as outlined in numerous other posts include, aerobic exercise, starvation diets (low calorie), sleep disturbance caused by odd work shifts, or decreased estrogen (numerous causes), stress of the working mother, nutritional stress (high carb / hypoglycemia), cell phone stress etc etc. The combination of these factors is causing dramatic changes in female physiology causing numerous symptoms and dysfunction of which fertility is only one of many.
Dr. Michael Fox, MD
Jacksonville Center for Reproductive Medicine
Advanced Reproductive Specialists
www.JCRM.org
https://www.today.com/health/menstrual-cycle-not-28-days-many-women-study-finds-t161373