Natural family planning

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Natural family planning chart and thermometer This page gives information on how natural family planning can help you to avoid pregnancy.

Fertility awareness involves being able to identify the signs and symptoms of fertility during the menstrual cycle so you can plan or avoid pregnancy.

Your Guide to Natural Family Planning (PDF)

The menstrual cycle is the time from the first day of your period to the day before your next period starts.

The average length of the menstrual cycle is around 28 days, although many women have longer or shorter cycles and this is normal. Regardless of how long or short the cycle is, ovulation (when the ovaries release an egg) will usually happen around 10–16 days before the start of the next period.

During your menstrual cycle:

  • Eggs develop in your ovaries and usually one is released.
  • The mucus in the cervix (entrance to the uterus – womb) changes to allow sperm to pass more easily through the cervix to reach the egg.
  • The lining of the uterus thickens to prepare for a pregnancy.
  • If the egg is not fertilised by sperm and you don’t get pregnant the uterus sheds its lining as your period, which signals the beginning of a new menstrual cycle.

The menstrual cycle is controlled by your body’s natural hormones – estrogen and progesterone.

Natural family planning works by observing and recording your body’s different natural signs or fertility indicators on each day of your menstrual cycle. The main fertility indicators are:

  • your body temperature
  • cervical secretions (cervical mucus)
  • the length of your menstrual cycle.

Changes in these fertility indicators can help you to identify your fertile time. You can also use fertility monitoring devices (see below, How do I use fertility monitoring devices?).

The fertile time lasts for around 8–9 days of each menstrual cycle. This is because the egg lives for up to 24 hours. Occasionally, more than one egg is released at ovulation (within 24 hours of the first egg being released) and sperm can live inside a woman's body for up to seven days. This means that if you have sex as much as seven days before ovulation you may get pregnant.

How effective any contraceptive method is depends on how old you are, how often you have sex and whether you follow the instructions.

If 100 sexually active women don't use any contraception, 80 to 90 will become pregnant in a year.

If used according to teaching and instructions, natural family planning methods are up to 99 per cent effective, depending on which method is used. This means that up to one woman in 100 will get pregnant in a year.

If natural family planning methods are not used according to instructions, more women will get pregnant.

Natural family planning is more effective when taught by a specialist natural family planning teacher, and when more than one fertility indicator is used.

Some people choose to combine their fertility awareness knowledge with male or female condoms – this is sometimes known as fertility awareness combined methods. The effectiveness of this depends on how well you use male or female condoms.

  • Using fertility awareness makes you more aware of your fertility and can help to plan a pregnancy or avoid a pregnancy.
  • There are no physical side effects.
  • It can help you recognise normal and abnormal vaginal secretions.
  • It can help you to communicate about your fertility and sexuality.
  • It is acceptable to all faiths and cultures.
  • It takes 3–6 menstrual cycles to learn effectively.
  • You have to keep daily records.
  • Some events, such as illness, lifestyle, stress or travel, may make fertility indicators harder to interpret.
  • You need to avoid sex or use male or female condoms during the fertile time.
  • Natural methods don't protect you against sexually transmitted infections (STIs).

Most women can use natural methods as long as they receive good instructions and support. They can be used at all stages of your reproductive life, whatever age you are. Natural family planning may not be a suitable method for women who do not have periods.

It may take longer to recognise your fertility indicators and to start to use natural family planning if you have irregular cycles, after stopping hormonal contraception, after having a baby, during breastfeeding, after an abortion or miscarriage, or when approaching the menopause.

Some natural methods rely on using only one of the fertility indicators. Other methods use two or more indicators – this is more effective.

Fertility indicator chart

© Copyright J Knight and C Pyper. Adapted from Fertility UK 2005.

Download a PDF of this fertility indicator chart (opens in new window)

The hormones estrogen and progesterone cause your body temperature to change throughout the menstrual cycle – it rises slightly after you have ovulated.

You can chart these changes by recording your temperature each day to show you when the fertile time ends. Visit to download a fertility chart. You should use a centigrade digital thermometer which has a last memory recall and a low battery warning indicator. Ear or forehead thermometers are not accurate enough to use for natural family planning.

You need to take your temperature before you get out of bed or after you have had at least three hours rest. This is known as your basal body temperature (BBT) or waking temperature. This should be done at the same time each day and before you have anything to eat or drink.

The fertile time ends when you have recorded temperatures for three days in a row, which are higher than all the previous six days. The difference in temperature will be about 0.2 degrees centigrade (0.4 degrees Fahrenheit).

Certain activities or events can alter your temperature readings and can make them less accurate. For example if you:

  • take your temperature earlier or later than normal
  • use poor equipment or record the findings badly
  • have an illness, such as a cold or flu, drink alcohol or oversleep (this can make your temperature go up)
  • are taking pain relieving drugs, including aspirin (this can make your temperature go down).

The temperature indicator on its own does not help you to find the start of your fertile time.

The amount of estrogen and progesterone varies in the menstrual cycle and this alters the quantity and type of cervical mucus. By monitoring the changes in your cervical secretions you can learn to identify the start and end of your fertile time.

  • After your period you may notice a few days when your vagina and vulva feels dry and you can’t see or feel any cervical secretions.
  • As the level of estrogen rises, your body prepares for ovulation and the secretions produced by the cervix begin to change in texture and increase in amount and sensation. At first they feel moist, sticky and appear white or creamy in colour. This is the start of the fertile time.
  • Just before ovulation the secretions become clearer, wetter, stretchy and slippery like raw egg white. This is known as fertile mucus and is a sign that you are at the most fertile phase of your cycle.
  • After ovulation the cervical secretions return to being thicker and sticky and after three days you will no longer be fertile.

The amount and quality of cervical secretions will vary from woman to woman and also from one cycle to the next.

Yes. Combining the temperature and cervical secretions indicators acts as a double check and increases the effectiveness of natural family planning.

The fertile time starts at the first sign of any cervical secretions and ends after the third high temperature has been recorded and all three high temperatures occur after the last day of having wet or clear, slippery secretions (the peak day).

The length of your cycles can help you to work out the start of your fertile time. Keep a record of the length of your last 12 cycles, then find your shortest cycle and subtract 20 days to find the first fertile day. Calculating your cycle length is not a reliable way of working out the end of your fertile time and should not be used on its own as a fertility indicator.

During your menstrual cycle your cervix changes in position and feels different.

Around your fertile time the cervix will feel higher in the vagina, soft and slightly open.

During your infertile time your cervix will feel low in the vagina, firmer to touch and closed. These changes are not reliable enough to be used on their own as a fertility indicator.

Some women may be aware of pain around ovulation or changes in the breasts, skin, mood or sex drive. These are the least reliable indicators of your fertile time.

You can buy a number of different fertility devices. They work by monitoring changes in temperature, urine or saliva.

In the UK the most widely available product is Persona. This consists of a handheld computerised monitor and a series of urine test sticks which measure hormonal changes. Persona interprets these changes and can predict the fertile and infertile times of your menstrual cycle.

If you use Persona according to the instructions, it is around 94 per cent effective. This means that at least six women in 100 will get pregnant in a year.

Computerised thermometers work by combining information about the length of your menstrual cycle and temperature. More research is needed about the effectiveness of these products.

Luteinising hormone (LH) dipstick tests or ovulation predictor kits are designed to be used by women planning a pregnancy. They are not effective as a natural family planning method.

Saliva testing devices are not accurate and should not be used for avoiding pregnancy.

There are numerous apps available for mobile phones and a number of online charting systems. These products vary in their approach using one or more fertility indicators. Their reliability and effectiveness in avoiding pregnancy is unknown.

Breastfeeding is also known as lactation. When used as a contraceptive method it can be very effective in avoiding pregnancy and is known as lactational amenorrhoea method (LAM).

LAM can be up to 98 per cent effective in preventing pregnancy if all of the following conditions apply:

  • you are fully breastfeeding – this means you are not giving your baby any other liquid or solid food or
  • you are nearly fully breastfeeding – this means mainly breastfeeding your baby and infrequently giving your baby other liquids and
  • your baby is less than six months old and
  • you have no periods.

The risk of pregnancy increases if:

  • you start breastfeeding less often or
  • there are long intervals between feeds – both day and night or
  • you stop night feeds and use supplement feeding.

Once your baby is over six months old, the risk of getting pregnant increases so, even if you don't have periods and are fully, or nearly fully breastfeeding, you should use another contraceptive method.

Yes. Using hormonal emergency contraception will upset your normal hormone pattern and alter your fertility indicators.

After using hormonal emergency contraception you should not rely on your natural family planning indicators for two complete menstrual cycles. This allows time for your cycle to return to normal and for your natural family planning indicators to be reliable.

You will need to find someone to teach you how to use natural family planning.

General practice and contraception clinics do not often teach it so you may need to find your own teacher – some charge a fee.

You can get further information from:

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This website can only give you general information about contraception. The information is based on evidence-guided research from the World Health Organization and The Faculty of Sexual and Reproductive Healthcare of the Royal College of Obstetricians and Gynaecologists. All methods of contraception come with a Patient Information Leaflet which provides detailed information about the method.

Remember – contact your doctor, practice nurse or a contraception clinic if you are worried or unsure about anything.