Fertility awareness

Fertility awareness (also known as natural family planning) is a method used to plan or prevent pregnancy by recognising the signs of fertility in your menstrual cycle.

On this page, you can find the following information:

Key points about fertility awareness

  1. You need to learn about your menstrual cycle and signs of fertility for this method to work. 
  2. You find out when you are likely to be fertile by tracking your menstrual cycle, ovulation, body temperature and cervical mucus. 
  3. You can use this method to plan or prevent pregnancy, but there are factors that affect fertility signs, making the method inaccurate. 
  4. If used perfectly, it can be up to 99% effective (only 1 in 100 will get pregnant), but in real-life usage the pregnancy rate is higher because of difficulties using it correctly.
  5. It's best to get training from a healthcare provider trained in this method. Ask your family doctor or GP where you can get this.

Use a barrier method of contraception, such as a condom, when you are still learning how to use the fertility awareness method. 

What is fertility awareness?

Natural family planning is a method used to plan or prevent pregnancy by recognising the signs of fertility in your menstrual cycle. 

How does fertility awareness work?

You will need to learn and understand your menstrual cycle and signs of fertility in order for this method to work. By understanding your menstrual cycle and how it causes some bodily changes, you can work out when you are fertile and when not to have sexual intercourse to prevent pregnancy. 

For the natural family planning method to work effectively, it's best that you get taught how to do it by a trained healthcare provider. Talk to your family doctor or GP to find out where you can get this.

What are the signs of fertility? 

You will need to learn the following to identify the signs of fertility:

  • the length of your menstrual cycle and time of ovulation
  • your daily body temperature
  • changes to your cervical secretions or cervical mucus. 

By learning these, you can then plan when to have sexual intercourse in order to plan or prevent pregnancy. 

Your menstrual cycle and ovulation

Your menstrual cycle lasts from the first day of your period until the day before your next period starts. The average cycle is 28 days long but it can be normal for your cycle to be shorter or longer (between 21–40 days). In the middle of your cycle, which is about day 14, an egg is released from one of your ovaries and travels down your fallopian tube. This process is known as ovulation and can happen a few days before or after day 14 (between days 10–16). Sometimes a second egg is released within 24 hours of the first egg. 

After your egg has been released, it can live in your body for around 24 hours. A sperm must meet your egg within the 24-hour period for pregnancy to happen. You can get pregnant up to 2 days after you ovulate because there is sometimes a second egg.

It's also possible to get pregnant if you have had sexual intercourse in the 7 days before your egg is released. This is because when a sperm enters your womb, it can live for up to 7 days. 

The length of your menstrual cycle can vary over time. For the best accuracy, keep track of your menstrual cycle over a period of 12 months. Then you can calculate when you are most likely to be fertile to prevent or plan a pregnancy. However, you need to allow for uncertainty over exactly when you ovulate. 

Your body temperature

After ovulation, your body temperature rises a little. The rise in temperature is very small, around 0.2° Celsius. Therefore, measuring your daily body temperature helps you to find out when you are or are not fertile. You need to use a digital thermometer or a thermometer specifically designed for natural family planning. Ask your local pharmacist, your nurse or your doctor for more details. 

You need to measure your temperature at the same time every morning before you get out of bed. If you notice your temperature is higher for 3 days in a row than the previous 6 days, then it's likely that you are not fertile at this time. However, there are a lot of factors that can also affect your body temperature, including:

  • medicines such as paracetamol
  • illnesses such as colds, flu or other infections.

Your cervical secretions or cervical mucus 

Your cervical secretions or mucus can change throughout your menstrual cycle. Your cervical mucus is moist, sticky, white and creamy as your hormone levels rise and your body is preparing for ovulation. Your fertile period starts around this time.

Then, immediately before ovulation, your mucus becomes clearer, wetter and slippery, like raw egg white. This is to allow sperm to swim through it to meet an egg. This is the time when you are most fertile.

After ovulation, your mucus will become thicker and sticky again, and you should no longer be fertile after 3 days. 

Use a barrier method of contraception, such as a condom, when you are still learning how to use the fertility awareness method. 

Who can use the fertility awareness method?

You can use this method to plan or prevent pregnancy. However, there are factors that can affect the signs of fertility, making the method inaccurate.

These include:

The natural family planning method is not recommended if an unplanned pregnancy would be a serious health risk, or if you are taking medicine that could be harmful in pregnancy.

How effective is fertility awareness at preventing pregnancy?

If used correctly, natural family planning can be up to 99% effective. This means out of 100 women who follow natural family planning perfectly for 1 year, only 1 will get pregnant. 

However, the actual pregnancy rate is higher in people who use the natural family planning method – somewhere between 2–23 pregnancies out of 100 women each year.

Some of the reasons for this include:

  • not being taught the method correctly
  • not understanding how to use the method
  • having difficulty recognising the signs of fertility
  • having sexual intercourse during the fertile time.  

What are the benefits of fertility awareness?

The benefits of natural family planning include:

  • no side effects
  • it's acceptable to all faiths and cultures
  • most women can use the method, as long as they get training 
  • it can be used either to plan or prevent pregnancy
  • no chemicals or products are involved
  • recognising normal and abnormal vaginal secretions makes you more aware of possible infection
  • improving the relationship between you and your partner as the method requires the commitment of your partner too. 

What are the disadvantages of fertility awareness?

Similar to other contraceptive methods, natural family planning has disadvantages if not followed correctly.

These include:

  • unplanned pregnancy
  • sexually transmitted infections if condoms are not used
  • much less effective at preventing pregnancy than other methods (such as long-acting reversible contraception) if not followed correctly 
  • it takes time for you to learn and be confident in identifying your fertile time
  • the need to practice and for continued commitment
  • the need to keep a daily record of your fertility signs
  • other factors affecting your fertility signs
  • the need to use other methods of contraception or avoid sex when you are fertile. 

What support is available with fertility awareness?

Natural Fertility NZ specialises in teaching individuals and couples about natural fertility and how it relates to the menstrual cycle. There are also education sessions for healthcare professionals. Phone 0800 101 637 or email admin@naturalfertility.co.nz to find out more details. 

Learn more

The following links provide further information about natural family planning. Be aware that websites from other countries may have information that differs from New Zealand recommendations. 

Resources for trying to conceive Natural Fertility NZ
Fertility awareness Family Planning NZ  
Natural family planning (fertility awareness) NHS, UK
Natural family planning methods Patient Info, UK


  1. NZ Aotearoa's guidance on contraception Ministry of Health, NZ, 2020
  2. Contraception information Auckland Regional HealthPathways, NZ, 2020
  3. Fertility awareness Family Planning NZ  
  4. Natural family planning (fertility awareness) NHS, UK
  5. Natural family planning methods Patient Info, UK

Reviewed by

Dr Alice Miller trained as a GP in the UK and has been working in New Zealand since 2013. She has undertaken extra study in diabetes, sexual and reproductive healthcare, and skin cancer medicine. Alice has a special interest in preventative health and self-care, which she is building on by studying for the Diploma of Public Health with the University of Otago in Wellington.
Credits: Health Navigator Editorial Team. Reviewed By: Dr Alice Miller, FRNZCGP, Wellington Last reviewed: 08 Mar 2021