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By Koparday's formula, calculation of fertile period is as follows
Your shortest cycle days minus 18 days=1st day of fertile period.
The longest cycle days minus 10 days= last day of fertile period.
Ex: If your menstrual cycle varies from 26days to 31days cycle,
The shortest cycle [26days] minus18days=8th day.
The longest cycle [31days] minus 10days=21st day.
Thus, 8th to 21st day of each cycle counting from first day of menstrual period is considered as fertile period.
Period other than this fertile period in a menstrual cycle is considered as SAFE PERIOD.
Answered: Wed, 15 Jun 2011
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