In perimenopausal women, menstrual cycle hormone patterns resemble those of midreproductive aged women until 5 years before menopause, a recent study found, with ovulatory cycles presumably retaining a potentially fertile pattern. This according to the Study of Women’s Health Across the Nation (SWAN) Daily Hormone Study (DHS) at 7 sites across the US. The study included 511 premenopausal or early perimenopausal women at enrollment, and within 10 years before menopause. Researchers found:

• Mean menstrual cycle length was preserved at 26-27 days in evidence of luteal activity (ELA) cycles; non-ELA cycles had greater variability.
• Percentage of cycles that were ELA remained high until 5 years before the final menstrual period (FMP) at 87.9%.
• Only 22.8% of cycles within 1 year of the FMP were ELA.
• Whole cycle hormones remained relatively stable up to 3 years before the FMP.