Feile period in a women with menstural cycle of 26-31 days ?

Ans. is 'a' i.e., 8-21 days of cycle Safe Period (rhythm method) This is also known as the calendar method first described by Ogino. The method is based upon the fact that ovulation occurs from 12 to 16 days before the onset of mensturation. Calculation is as follows : The shoest cycle minus 18 days gives the first day of the feile period. The longest cycle minus 10 days gives the last day of feile period. For example, if a woman's menstural cycle varies from 26-31 days, the feile period during which she should not have intercourse would be from the 8th day to 21st day of the menstural cycle, counting day one as the first day of the menstural period.