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.