Women's Health Matters

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Fertility awareness

Fertility awareness relies on tracking a woman’s fertile times, and either avoiding intercourse or using a barrier method of birth control on fertile days.

Every month, changes in a woman’s hormone levels direct her body to release an egg from the ovaries. In order for a woman to get pregnant, this egg must be fertilized by a man’s sperm within about 24 hours of its release from the ovaries. However, even though an egg’s lifespan is only a day or so, sperm can live in a woman’s body for up to five days. That means that a woman can become pregnant if she has intercourse several days before ovulation, because sperm may still be active when she ovulates.

Fertile days

The days in a woman’s menstrual cycle when she is most likely to become pregnant are called her fertile days. There are about seven to 10 fertile days per cycle: about five days leading up to ovulation, the day she ovulates, and a day or two after ovulation.

To avoid pregnancy, a woman must either avoid intercourse, or use another method of birth control – such as a condom, diaphragm or sponge – on these days.

In order to know which days are her fertile days, a woman must get to know her menstrual cycle and learn to monitor when she is ovulating. Fertility awareness may not be a good choice for women with irregular menstrual cycles.

The menstrual cycle begins on the first day of a woman’s period. This is Day 1, when hormone levels are at their lowest. In an average-length cycle, ovulation usually occurs around Day 14. Estrogen levels are highest at ovulation.

In order to use the fertility awareness method to prevent pregnancy, a woman needs to track physical symptoms that indicate her hormone levels, and keep track of her menstrual cycles. There are several approaches to this.

A woman can track ovulation by:

  • taking her temperature every morning before getting out of bed
  • monitoring changes in her cervical fluid

The fertility awareness method is most effective when these are used in combination. This is called the sympto-thermal method.

Other types of fertility awareness methods used for birth control are based on calendars. These may be simpler to follow, but may not be as accurate in predicting ovulation as tracking daily symptoms.

If used perfectly and consistently, the effectiveness of fertility awareness can be as high as 99 per cent for women who never have intercourse during their fertile time. However, in typical use, effectiveness of fertility awareness can be as low as 75 per cent.

For fertility awareness methods to work, both partners must be committed to either not having intercourse on fertile days, or using another method of birth control on those days.  

Fertility awareness is also useful for women who want to get pregnant. By identifying her most fertile days, a woman can time intercourse for the days when she is most likely to conceive.

Fertility awareness does not offer protection from sexually transmitted infections.


  • low cost
  • no side-effects
  • encourages women to get to know how their bodies work
  • compatible with most religious beliefs 
  • requires commitment from both partners


  • not highly effective with typical use
  • requires time and attention to learn
  • requires ongoing daily attention from the woman to track symptoms
  • must avoid intercourse or use another birth control method for several days every month
  • not a good choice for women who are not comfortable with their bodies
  • not a good choice for women with irregular cycles
  • does not protect against sexually transmitted infections
  • requires commitment from both partners
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  • A publication of:
  • Women's College Hospital