The menstrual flow or menses (also called the period) is the external sign that the lining of the womb (or endometrium) is sloughing. The beginning of the menses is considered the first day of the menstrual period and usually the greatest flow is on the first and second day of the menses, after that the flow begins to taper off. Speroff and Fritz (2005, p. 549) define a normal menstrual period to be about 4-5 days long occurring approximately every 24 to 35 days. Management of unusual bleeding, which occurs outside of a normal menses, is to consider those days with unusual bleeding as fertile. If this occurs more than three consecutive cycles please contact your NFP nurse. See instructions below for managing unusual bleeding with cervical mucus monitoring. (Example Unusual Bleeding).
First 6 cycles
After 6 cycles, fertility BEGINS on the earliest day of “peak” type mucus during the last 6 cycles minus 6 days or the first "high" mucus reading or any bleeding outside of the menses – whichever comes first.
THE END OF FERTILITY:
Fertility ENDS on the last “peak” day of cervical mucus plus 3 full days.
After 6 cycles, fertility ENDS on the last “peak” day of the last 6 cycles plus 3 full days, or the last "peak" day of cervical mucus plus a count of 3 full days - whichever comes first.
Speroff, L & Fritz, M (2005) Clinical Gynecologic Endocrinology and Infertility (7th Ed.) Philadelphia, Lippincott Williams & Wilkins