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Natural is Rythm method of contraception
.. In this method from 1st to 8th day and 22nd to 28th day of menstrual cycle is safest.. intercourse during this period will no result in pregnancy
... Because the normal ovulation time is 14th day of cycle, but it can occur 2days before or after, and the life span of sperm in the female genital tract is 24hrs hence coitus at 10th day 18th day and can also result in pregnancy... Hence the safest period is between 1st to 8th day and 22nd to 28 day of Normal menstrual cycle..