How to avoid pregnancy using the Rhythm method or the calendar method

The rhythm method, also known as the calendar method, is a natural form of birth control that involves a woman monitoring her menstrual cycle and avoiding unprotected intercourse during her most fertile days each month. Some women prefer it to medicated birth control or barrier methods for religious reasons or because they see it as a more natural way of managing their fertility.

Instructions

1

Calculate the length of your last 12 menstrual cycles. This is the number of days between the first day of one period, counted as day one, and the day before your next period begins, which counts as the last day of your cycle.

2

Write the length of each cycle down in a table. Make two columns in the table. Write the date of the first day in each cycle in the left-hand column, and the number of days in the cycle in the right-hand column.

3

Select the shortest cycle length in your table and take away 18 from the number. The resultant number is the first day of your fertile time and the first day you should avoid unprotected intercourse. For example, if your shortest cycle is 26 days long, you should subtract 18 to get 8. This means that the eighth day of your cycle is the start of your most fertile time.

4

Select the longest cycle from your table and subtract 11 from that number. The resultant number marks your last fertile day. For example, if your longest cycle was 32 days, subtract 11 to get 21. In this example, you should avoid unprotected intercourse between the eighth and twenty-first days of your menstrual cycle.

5

Keep recording the lengths of your menstrual cycle to make sure your calculations are up to date. Menstruation can be affected by stress, illness and medication so its important to keep your records updated.