|  | Family Health | Womens Health

Using the Calendar Method to Determine Fertile Days

The calender method, also referred to as the rhythm method, is a way for couples to chart the time in a woman's cycle when she's most likely to become pregnant. This method works well for women who don't tolerate hormonal birth control well or who choose to opt for a more natural means of pregnancy prevention. It's also a useful tool for couples who are trying to conceive, as it helps pinpoint a woman's fertile days.

  1. Measuring Your Cycle

    • This method is most accurate when it's done over the course of at least six to 12 months. The fewer months recorded, the less accurate the results; however, women who have highly regular cycles can be reasonably sure of their fertile time within two to three months. To measure your cycle, mark the date you begin your period as day one. When you get your next period, mark the first day, again, as day one. Number the days in between to find out how long your cycle was. Repeat each month.

    Calculating Ovulation

    • Once you have six to 12 months of cycle data recorded, you can now use these numbers to predict your most fertile times. Write down the numbers that correlate with your longest and shortest cycles. Subtract 18 from the length of your shortest cycle. This number represents the first day of your fertile time. Subtract 11 from the length of your longest cycle, and this represents the last day of your fertile time. For example, if your shortest cycle was 26 days long, and your longest cycle was 29 days long, your fertile period would be from approximately the 8th to the 18th day.

    Advantages and Disadvantages

    • This method has both its advantages and disadvantages. It's free for women who can't afford other methods of birth control. It also involves no prescriptions and has no costs associated with it. It can be used in addition to family planning methods you're already trying, and for women with regular cycles, it can be very accurate. The disadvantages are that it's not as effective as hormonal birth control, which is 99.9 percent effective when taken correctly. Unlike other forms of birth control, this method requires a backup method, like condoms, during fertile times to prevent pregnancy. A woman's cycles can also change at any time for any number of reasons, so this method is best used as an estimate and not an absolute.

Womens Health - Related Articles