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Dear Kathy:
The first day of a menstrual cycle is the first day of "real bleeding". Spotting belongs to the end of the previous cycle.
Ovulation occurs in all the books 14 days before the menstrual flow. Thus, in a 21 day cycle, ovulation occurs on average on day 7. The second half of the menstrual cycle may the 14 days in books, but it can be as short as 10 days and as long as 16 days in real life. Thus, in a 21 day cycle, ovulation could occur as early as day 5 (the uterine lining is probably not ready to be a good host) or as late as day 11.
Keywords: length of menstrual cycle.
This information is provided for education purposes and is not a medical consultation. If you have specific questions, please speak with your healthcare provider.
Menstrual cycles that range between 21 and 35 days are considered normal. Longer and shorter cycles are considered abnormal.