15 min read

Natural family planning

Medically reviewed

All of Healthily's articles undergo medical safety checks to verify that the information is medically safe. View more details in our safety page, or read our editorial policy.

What is natural family planning?

Natural family planning is when natural signs, such as body temperature, are used to identify when a woman is at her least and most fertile during each menstrual cycle, to help either avoid or plan pregnancy. This is known as fertility awareness.

There are a number of ways to assess whether it is likely that you are currently fertile. You can:

  • calculate where you are in your menstrual cycle (how long since your last period) – most women ovulate (produce an egg that is ready for fertilisation) 10-16 days before they have their period
  • check the consistency of the mucus in your cervix (the opening to the womb) –if the mucus looks white and creamy in colour it is normally a sign that you are fertile
  • take your temperature daily – if your temperature rises above normal for a few days it is usually a sign that you are no longer fertile

Read more about how natural family planning is performed.

Is it reliable?

In theory natural family planning can be up 99% effective in preventing unwanted pregnancies.

However, in practice natural family planning can be a complex procedure and it’s often possible to make a mistake when assessing fertility.

In reality natural family planning is estimated to be around 75% effective - so 1 in 4 women using this method of birth control may still become pregnant.

The same is also true of other methods of birth control. For example, male condoms are, in theory, 98% effective in preventing unwanted pregnancies, but in reality it’s more like 85% - so around 1 in 7 women using still become pregnant.

Read more about the results of natural family planning when compared to other methods of birth control.

Who can use it?

Provided it’s followed correctly (usually with proper instruction from a trained natural family planning teacher) most women can use natural family planning effectively. There may be circumstances in which it is not recommended as a form of birth control, including:

  • if you had a serious health condition that could be made worse if you became pregnant, or alternatively could place the life of any baby you had at risk, such as heart disease – a more reliable method of birth control would usually be recommended
  • if you had a condition that could disrupt your normal reproductive cycle such as polycystic ovary syndrome or cervical cancer

Natural family planning requires commitment from both members of a couple so it may only be suitable for you if you are currently in a stable relationship.

Read more about who is best suited to using natural family planning.

Pros and cons

Advantages of natural family planning include:

  • it does not cause any side effects
    once the techniques have been learnt
  • there should be no further input from health professionals
  • natural family planning is acceptable to all faiths and cultures

Disadvantages of natural family planning include:

  • natural family planning does not protect against sexually transmitted infections (STIs) such as chlamydia or HIV
  • you will need to abstain from sex during the fertile time of your menstrual cycle which some couples can find difficult
  • it is not as effective , as other forms of birth control, such as the contraceptive implant

Read more about the pros and cons of natural family planning.

How does natural family planning work?

It is important that you are taught natural family planning by a suitably qualified teacher.

The information in this section is designed to serve as an overview only. It is not a substitute for proper instruction and training.

Fertility awareness

The key to natural family planning is to use the signs and symptoms of your body to assess if you’re currently fertile and likely to get pregnant if you have sex.

Three different methods are used in combination to increase the effectiveness of this form of birth control. These are:

  • calculating where you are in your menstrual cycle
  • taking daily readings of your body temperature
  • monitoring changes to your cervix; specifically the secretions of mucus from your cervix

Each method is discussed in more detail below.

Your menstrual cycle

Your menstrual cycle lasts from the first day of your period up to, but not including, the first day of your next period. The length of a woman’s menstrual cycle can vary. Anything from 24 to 35 days is common, although it could be longer or shorter than this. On average, it lasts 28 days.


During your menstrual cycle, hormones are released to stimulate your ovaries. An egg stored in your ovaries begins to grow and mature. When the egg is mature, it’s released from your ovaries (ovulation) and travels down the fallopian tubes.

Occasionally, more than one egg is released.

Ovulation occurs roughly halfway through your menstrual cycle, usually around 10 to 16 days before the start of your next period.

Hormones will also cause the lining of your womb to thicken in order to receive the egg. If the egg isn’t fertilised with sperm, the lining of your womb will break down leading to a period.

An egg can only survive for 24 hours but sperm can survive in your womb for up to seven days, so depending on how soon ovulation followed ejaculation your may be fertile for up to eight days.

When calculating your fertile time, you need to take into account the uncertainty over exactly when you release eggs during your menstrual cycle,.

As the length of a menstrual cycle can vary over time, to ensure your calculations are as precise as possible you will need to measure your menstrual cycle over the course of six months.

One way of doing this is known as the calendar method, which .involves the following steps:

  • record the length of your menstrual cycle every month for six months; this is the number of days from the first day of your period to the first day of your next period; this is usually 28 days but can sometime vary a few days either side
  • take the length of your shortest cycle and the length of your longest cycle
  • subtract 18 days from the length of your shortest cycle - this is the first day of your fertile period
  • subtract 11 days from your longest cycle - this is the last day of your fertile period
  • do not have sex from the first day to the last day of your fertile period

For example if your shortest cycle was 25 days and your longest cycle was 33 days:

  • you would take away 18 from 25 to give you 7 days
  • you would take away 11 from 33 to give you 22 days
  • so you should avoid having sex from day 7 to day 22 of your menstrual cycle

The temperature method

The temperature method is based on the fact that there is a small rise in body temperature after ovulation takes place.

You will need to use either a digital thermometer or a thermometer specifically designed to be used for natural family planning, these are available from pharmacies. Ear or forehead thermometers are not accurate enough to be used in this way.

The temperature method involves:

  • you take your temperature every morning before getting out of bed, this should be done before eating or drinking anything, before smoking and ideally at the same time every morning
  • look out for three days in a row when your temperature is higher than all of the previous six days – the increase in temperature is very small; usually around 0.2C (0.4F) – it is likely that you are no longer fertile at this time

Monitoring your cervix

There is a change in the consistency and amount of the mucus secreted from your cervix during different times in your menstrual cycle.

You can check this by gently placing your middle finger into your vagina and pushing it up to around your middle knuckle.

For the first few days after your period you will probably find that your vagina is dry and you cannot feel any mucus. As the levels of hormones rise to prepare your body for ovulation, you will probably find that your cervix is now producing mucus that is moist and sticky and is white and creamy in colour. This is the start of the fertile period of your menstrual cycle.

Immediately before ovulation the mucus will get wetter, slippery and clearer; much like raw egg white. This is when you are at your most fertile.

The mucus should then soon return to being thicker and sticky and after three days you should no longer be fertile.

Combining methods

There are a number of factors that can disrupt normal fertility signs (see below) so relying on just the one method is not recommended.

It is best to combine the all three methods to give you a more accurate picture of when you are likely to be most fertile.

There are fertility charts that allow you to record information from all three methods which you can then track over the course of each menstrual cycle.

An example of fertility charts and information on how to use them can be found at the Fertility and Education website.

There are also a number of apps you can download for smartphones or software for your computer that allow you to track this information.

Things that affect your fertility signs

Your fertility signs can be disrupted if you:

Other factors that affect your body's natural signs include:

  • altering how and when you take your temperature
  • drinking alcohol
  • taking certain medication
  • being ill

Read more about who may not be suited for natural family planning.

Ovaries are the pair of reproductive organs that produce eggs and sex hormones in females.

Pro's and cons of natural family planning

The pros and cons of using natural family planning as a method of birth control are described below.


The advantages of using natural family planning methods include:

  • most women can use them, providing they are properly trained by a teacher in fertility awareness and keep accurate records
  • you do not need any further help from a healthcare provider once you have learnt how to use them
  • they can be used to avoid pregnancy or to become pregnant, according to your wishes
  • they do not involve chemicals or physical products, so there are no adverse side effects
  • they can help you recognise normal and abnormal vaginal secretions, so you are aware of any sexually transmitted infection
  • they are acceptable to all faiths and cultures
  • they involve your partner in the process which can often help increase feelings of intimacy and trust
  • they are immediately reversible - as soon as you stop using the methods, you can get pregnant (unlike the contraceptive injection, where your fertility can take a while to return)


The disadvantages of using natural family planning methods include:

  • they are much less effective in real world setting compared to other types of birth control; as many as 1 in 4 women using them will conceive within one year
  • they will not work without the continuing commitment and cooperation of both yourself and your partner
  • to be most effective you will need to be taught by someone trained in natural family planning
  • it can take several menstrual cycles before you can become confident in identifying your fertile time – this can be 2-3 cycles for measuring body temperature and monitoring your cervix and up to six cycles for using the calendar method - during this time you will have to use barrier contraception
  • it is not suitable if you have persistent irregular periods
  • you will need to keep daily record of your fertility signs
  • factors such as stress, illness, travel, lifestyle and use of hormonal treatments can disrupt your fertility signs. This includes oral emergency contraception, if you use this you will need to wait for 2 complete cycles before relying on NFP again.
  • during your fertile time you will either need to abstain from sex or use a barrier method of contraception
  • if you do decide to abstain it can sometimes be up to 16 days during which you cannot have sex – this can sometimes cause problems in a relationship

What is the effectiveness of natural family planning?

The effectiveness of birth control methods are measured in two ways, perfect use and typical use.

A perfect use measurement is based on how effective the birth control method would be if the instructions for use were followed exactly as recommended.

However in the real world people can make mistakes, forget instructions and other problems can occur. So a typical use measurement is based on what you’d expect to see in a more realistic setting.

The perfect use percentage of natural family planning is very good at 99%; out of a 100 women using that method only one would become pregnant.

But the typical use percentage – possibly due to the complexities involved – is less effective at 75%; out of a 100 women using that method 25 would become pregnant.

The perfect and typical use percentages of other types of birth control are listed below:

  • contraceptive pill (both the combined pill and the progestogen-only pill) – perfect use is 99.7% and typical use is 91%
  • contraceptive injection – perfect use is 99.7% and typical use is 97%
  • contraceptive implant – both the perfect and typical use are the same at 99.5%
  • contraceptive patch or ring – perfect use is 99.7% and typical use is 91%
  • intrauterine device (IUD)or IUS) (‘the coil’) – perfect use is 99.4% and typical use is 99.2%
  • male condom – perfect use is 98% and typical use is 85%
  • female condom – perfect use is 95% and typical use is 79%

If you do decide to use natural family planning you can reduce your risk of accidental pregnancy by making sure you are taught natural family planning by a suitably qualified teacher and then ensuring you follow their instructions and advice.

Who can use natural family planning?

Most women are able to use natural family planning. However, there are a number of circumstances where it is not recommended as a form of birth control, or as your only form of birth control.

These are described below.

  • You have a medical condition that makes becoming pregnant dangerous – such as poorly controlled high blood pressure](yourmd:/condition/blood-pressure-high) or [heart disease. Or there could potentially be a health risk to the baby if you did conceive, such as being dependent on drugs and /or alcohol, or taking medications known to cause birth defects. A more reliable method of birth control such as the contraceptive injection or implant would be recommended.
  • You are having irregular periods so predicting your fertile time period may be hard or impossible. Irregular periods can have a wide range of causes, such as age (both younger and older women are more prone to irregular periods), stress, rapid weight gain or loss, excessive exercise and having an overactive thyroid gland.
  • You have a temporary condition that is disrupting the normal signs of fertility which make using fertility awareness methods difficult to use, such as pelvic inflammatory disease, sexually transmitted infection (STI) or bacterial vaginosis – you would have to wait until the infection passed before using natural family planning.
  • You have a long-term condition (or other underlying factors) that is disrupting the normal signs of fertility, such as liver disease, an underactive](yourmd:/condition/thyroid-under-active) or overactive thyroid gland or [cervical cancer. Recently giving birth or having an abortion can disrupt the signs of fertility.
  • You are taking a medication known to disrupt the normal production of cervical mucus making fertility awareness methods difficult to use – this can include lithium (used to treat a number of serious mental health conditions, such as bipolar disorder) and some older types of antidepressants.
  • You have an increased risk of catching a sexually transmitted infection – for example you have multiple sexual partners, or are planning to travel to a part of the world where sexually transmitted infections are widespread, such as sub-Saharan Africa.
Content supplied byNHS Logonhs.uk
Was this article helpful?

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.