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Fertility Awareness

How It Is Done continued...

To find the last day that you are likely to be fertile, subtract 11 from the number of days in your longest menstrual cycle. Your last fertile day should be that many days after your menstrual bleeding begins. For example, if your longest menstrual cycle lasts 31 days, you would subtract 11 from 31 to get 20; your last fertile day would then be the 20th day after menstrual bleeding begins.

Sperm can live in your vagina 3 to 5 days after sex.

  • If you want to become pregnant, have sex every day or every other day from your first fertile day to your last fertile day.
  • If you do not want to become pregnant, do not have sex or be sure to use another method of birth control for 1 week before your first fertile day. In the example above, your fertile period is from day 8 to day 20, so protect yourself from becoming pregnant for these 12 days of your cycle.

The calendar method of birth control is not the best choice for women who have short, long, or irregular menstrual cycles. For this reason, the calendar method alone is never recommended for birth control. It must be used in combination with other birth control methods.

Standard days method (SDM)

On the first day of your period, move the ring to the red bead (day 1) on the CycleBeads. Count each day as one bead. On days 1 to 7, you can have unprotected sex. On days 8 to 19, do not have sex or be sure to use another method of birth control to avoid pregnancy. From day 20 to the end of your cycle, you can have unprotected sex. All brown beads are days when you are not likely to become pregnant. All white beads are days you are likely to become pregnant. The dark brown bead marks day 26 and the last brown bead before the red bead is day 32. The SDM works best for women who have cycles between 26 and 32 days long.

Basal body temperature (BBT) method

Take your temperature every morning for several months just after you wake up. Do it before eating, drinking, or doing any other activity. Use a special ovulation thermometer or digital thermometer that shows tenths (0.1) of a degree. Your temperature may be taken orally or rectally, but be sure to use the same location and the same thermometer each time. Leave the thermometer in place for a full 5 minutes. Record your temperature, then clean the thermometer and put it away. Any activity can change your basal temperature. Record your temperature on a chart or graph. Use a tracking chart with either Fahrenheit temperatures(What is a PDF document?) or Celsius temperatures(What is a PDF document?) to keep track of your temperature. Ovulation usually causes your BBT to rise by 0.4°F (0.2°C) and to stay high for over a week.

WebMD Medical Reference from Healthwise

Last Updated: December 07, 2011
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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