The main points

  • Natural Family Planning (NFP) refers to observing physical changes in the menstrual cycle to avoid having sex at the most fertile time of the month
  • NFP may only be 75% effective in preventing pregnancy
  • NFP does not provide protection against STIs

What is it?

Natural Family Planning (NFP) refers to noticing the physical changes that happen during your menstrual cycle so you know when to avoid having sex and can reduce your risk of becoming pregnant.

You can also use it to find out the best time to have sex to maximise your chances of becoming pregnant.

How effective is it?

NFP takes a lot of practice. There are several methods, some of which are more effective than others. Effectiveness depends on which method you use and how well you use it. If you use the most effective method, and use it correctly every time you have sex, it is 99% effective.

If you use the least effective method and mistakes happen, it may be only 75% effective at preventing pregnancy. That means that if 100 women used NFP to prevent pregnancy for a year, up to 25 would become pregnant.

NFP becomes more effective the longer you use it and the more motivated you are to avoid a pregnancy. Any sex outside the rules increases your chance of becoming pregnant.

How does it work?

You are potentially fertile and able to conceive a pregnancy in the days leading up to ovulation (releasing an egg) through until three days afterwards. NFP helps you recognise when these days are happening so you can avoid sex during this time.

How do I use it?

There are several different methods of NFP that can help you work out when you are at a low risk of pregnancy. These include:

  • monitoring changes in the mucus (sticky discharge) produced by the cervix (entrance to the womb), usually by recognising a wet sensation
  • monitoring your temperature changes
  • calculating your ovulation dates based on the time between one period and the next (this is the least effective NFP method)
  • using commercial products that can help you to determine your pregnancy risk.

You must be taught how to use these methods by a specialist in NFP. They may recommend using a combination of methods to reduce your risk of becoming pregnant.

What stops it from working?

If you have irregular periods, are breastfeeding, or nearing menopause, it can be difficult to work out when you are likely to become pregnant. Vaginal infections, illness, having sex, and stress can also affect accuracy.

What are the advantages?

  • NFP is totally natural and uses no chemicals.
  • It keeps you in touch with your body’s natural rhythm.
  • It helps you avoid or plan pregnancy.
  • It is effective if used strictly.
  • It involves both partners.

What are the disadvantages?

  • NFP may take up to six cycles to learn.
  • You won’t be able to have sex for a number of days during each menstrual cycle.
  • You must keep daily records, at least initially, depending on the method you use.
  • Many women feel most like sex during their fertile times (when NFP rules say not to have sex). NFP does not provide protection against sexually transmissible infections (STIs).

Who shouldn't use it?

There are no medical reasons that would stop you from using NFP. If you are considering using NFP, you should think carefully, as it requires a fair amount of effort to master and has a high failure rate if not used correctly every time. This is particularly important if you have a medical condition that makes pregnancy risky.

What are the side effects?

There are no side effects.

Is it for me?

NFP may be right for you if:

  • you want contraception without artificial devices or chemicals
  • you have regular periods 
  • an unexpected pregnancy would not be disastrous for you (NFP is not 100% effective at preventing pregnancy) 
  • you and your partner are both motivated and willing to avoid sex at the most fertile times in your menstrual cycle.

NFP might also be right for you if you are trying to become pregnant - to help identify when you are most fertile.

What if I become pregnant?

NFP cannot harm a pregnancy.

Can I use NFP with other methods?

Condoms and diaphragms can be used with NFP if you want to have sex at fertile times, though these methods of contraception may make identifying the symptoms of ovulation more difficult to interpret. NFP cannot be used with hormonal contraception.

Other things you should know

  • If you are unsure whether it was a safe time or not and you have had sex and don’t want to become pregnant, you should use emergency contraception.
  • Emergency contraception may change your bleeding pattern, and this may affect the reliability of the NFP method.


You should discuss any further questions with your NFP specialist or call your local family planning clinic. If needed, one form of emergency contraception is available from pharmacies without the need for a doctor’s prescription. Another more effective form of emergency contraception is available only with a doctor’s prescription.

Where to get more information, support or advice

This information has been produced in consultation with and approved by: Better Health Channel

Better Health Channel


This website provides general information only. The suitability of such general information  varies  from   person  to   person,  depending  on individual circumstances.   You should seek specific medical or legal advice for your individual circumstances.

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Last updated: 5 June 2016

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