Calendar Method
What is it?
The calendar method helps you estimate the time of ovulation after you have charted the lengths of your menstrual cycles for several months.
How to Use
- Keep track of the lengths of your menstrual cycles for 6-12 months. Day 1 is the first day of your menstrual bleeding.
- After six or twelve months of data collection, find the length of the shortest and longest menstrual cycle.
- Subtract 18 from the length of your shortest cycle. This tells you the first fertile day in your average cycle. For example, if your shortest cycle is 24 days long, then your first fertile day would be day 6 of your cycle.
- Subtract 11 from your longest cycle. This will be the last fertile day in your average cycle. For example, if your longest cycle was 32 days long, then your last fertile day would be day 21 of your cycle.
- During this fertile period (e.g., Day 6 through Day 21) you must abstain from having unprotected intercourse.
Advantages
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