menstrual cycle

What is natural family planning?

Natural family planning is a birth control option that involves abstaining from having sexual intercourse during the time that you are most likely to become pregnant. It is also sometimes referred to as ‘fertility awareness-based methods of contraception’ or ‘periodic abstinence’.

How does it work?

The natural family planning method works by determining your fertile days by observing changes in your basal body temperature (BBT) or cervical mucus, or by using sympto-thermal (involving ovulation symptoms and temperature observation) or calendar methods, and by refraining from intercourse during those days.

Because some sperm can survive for as long as 7 days (the average is 2-3 days), and eggs for up to 24 hours after release from the ovary, most women are fertile for a few days before and after ovulation, and this must be taken into account in determining the period of abstinence.

How effective is natural family planning?

The effectiveness of natural planning methods can vary enormously, depending on the particular technique used, and the commitment of the couple.

Effectiveness can be measured for perfect use and typical use.

  • Perfect use is when instructions are followed precisely. Failures during perfect use represent failure of the method itself. Reported failure rates for perfect use range from less than one per cent to 5 per cent.
  • Typical use is what tends to happen in reality. Typical use failures include failures due to incorrect use of the method. Failure rates range from 2 to 25 per cent.

When used for a year by 100 women, the different methods below have the following typical use failure rates.

Typical use failure rates
Temperature method 14-25 pregnancies
Cervical mucus method 3-22 pregnancies
Sympto-thermal method 2-8 pregnancies
Calendar method an estimated 8-25 pregnancies


Some of the advantages of natural family planning are that:

  • it does not require medicines, chemicals or devices;
  • there are no health risks;
  • it is approved by many religions;
  • it is inexpensive;
  • it can encourage communication and co-operation in motivated couples; and
  • it allows a woman to become aware and informed of her reproductive cycles.


Some of the disadvantages of natural family planning are that:

  • it requires extensive instruction and many steps to predict ovulation (fertile period);
  • couples must be highly motivated;
  • it may result in periods of sexual frustration during periods of abstinence;
  • it does not offer protection against sexually transmitted infections (STIs);
  • since the length of menstrual cycles and the day of ovulation may vary each month, the timing of intercourse must be adjusted accordingly;
  • accurately predicting ovulation can be difficult;
  • it may not be suitable for women with irregular periods or those approaching menopause;
  • some indicators of fertility can be altered by illness, stress and having sex; and
  • in practice, it is often not as reliable as other methods of birth control.


The way that you use natural family planning depends upon the method you choose to monitor your menstrual cycle.

Temperature method

To use the temperature method, you should take your basal body temperature (BBT) at the same time every day upon waking, and before getting out of bed, eating or drinking. This can be done vaginally, rectally or orally (the least accurate) with a special basal or ovulation thermometer that can give an accurate measurement to within one-tenth of a degree (0.1 Celsius).

Factors that can skew these recordings include:

  • sleeping in;
  • having too little sleep;
  • illness;
  • consuming alcohol the night before;
  • stress;
  • shift work;
  • travel and time zone differences;
  • certain medicines; and
  • using an electric blanket.

If you chart your daily temperature, you will notice that following ovulation your BBT will rise by 0.2-0.5 degrees Celsius. Once you have recorded temperature rises for 3 consecutive days (all of which exceed the previous 6 recordings), you can safely have intercourse. This means that you can only have sex in the phase of your menstrual cycle after ovulation (i.e. for about 12 out of 28 days).

Cervical mucus method

To use the cervical mucus method, you must learn to distinguish between your fertile and infertile days on the basis of the type of cervical mucus being produced by your body. During the first part of your cycle (immediately after your period — the infertile phase) you will have a feeling of vulval dryness. This is followed by a period of vulval wetness, where your body produces clear, stretchy, slippery mucus, which corresponds to ovulation (fertile phase). The post-ovulatory phase then occurs when progesterone is produced, which causes the vulval area to have thicker, cloudier mucus, before returning to dryness once again.

You should mark these changes on a chart, indicating your fertile peak (last day of the slippery mucus) with a cross and numbering the 3 days following it. When trying to avoid pregnancy, you should not have sexual intercourse during this fertile phase, and until 3 consecutive dry days have passed. You should not have sexual intercourse during your period. Also, if you have sex after your period and before the fertile peak it should only be on alternate evenings where no mucus is present, otherwise the semen will make it impossible to determine the status of your mucus.

The cervical mucus method is not reliable for women who have abnormal vaginal bleeding or inflammation of the cervix or vagina. Cervical mucus signs are also difficult to read in women taking certain medicines (e.g. antibiotics, antihistamines, thyroid medicines) that can change the nature of vaginal secretions.

Sympto-thermal method

This method uses a combination of the above two techniques, with temperature being taken in the morning, and mucus being examined in the evening. Sometimes it is used in conjunction with other signs of ovulation, such as mid-cycle pain, spotting or breast tenderness.

Calendar (rhythm) method

This method is based on the assumption that ovulation takes place 12-16 days before your period starts. Knowing the length of your last 6 menstrual cycles, you can use this information to roughly predict when you should abstain from sexual intercourse. This method is generally not recommended on its own because of its unreliability, especially if you have irregular menstrual cycles.

Talk to your doctor about whether natural family planning is appropriate for you and to get further information, education and training on natural family planning methods.

Last Reviewed: 11/08/2013

myDr. Adapted from original material sourced from MediMedia.


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