You can get pregnant any time ovulation happens (when an egg is released). This is usually followed by a period, so starting your periods (monthly bleeding or ‘menstruation’) is a sign that your body is capable of carrying a baby.
But you may even be able to get pregnant before this happens, and sometimes this exact time can be hard to predict. This means you could get pregnant any time you have sex – even if it’s your first time having sex, and even if you've never had a period.
Changes that happen during your monthly menstrual cycle affect your chance of pregnancy. Read on to learn about when you’re more likely to get pregnant and how this can help you avoid or plan a pregnancy.
However, if you do not want to get pregnant, it’s important to use an effective contraception method. It is also worth knowing that the only contraception method that will protect against both pregnancy and sexual infections is condoms.
What are my chances of getting pregnant?
Over the course of your monthly menstrual cycle, your body goes through changes that make you more likely to get pregnant – or more ‘fertile’ – at certain times.
This means that if you’re familiar with your cycle, you may be able to work out when you’re most fertile. However, it’s important to remember that menstrual cycles can be unpredictable and irregular – there are no definite ‘safe’ days where there’s no chance of pregnancy.
The ‘fertility window’
Your cycle runs from your first day of period bleeding to the day before your next period starts. An average cycle lasts about 28 days, though lots of people have slightly shorter or longer cycles.
Whatever the length of your cycle, you’ll usually release an egg from your ovaries about 10-16 days before the start of your period. This is known as ‘ovulation’.
If the egg meets sperm from a penis, it can be ‘fertilised’, and you can get pregnant. Your most fertile time, or ‘fertility window’, is from about 7 days before ovulation to 2 days after ovulation.
Your fertile time starts before you release an egg because sperm can live inside you for up to 7 days after you have sex. A released egg can only live for about a day if it isn’t fertilised, but occasionally you’ll release a second egg within a day of the first.
This means that your fertile window lasts for about 8 to 9 days of your cycle. During this time, your chances of getting pregnant are roughly between 10% and 33%.
How do I work out when I’m fertile?
Using a combination of different ‘fertility awareness’ methods (also known as natural family planning) can help to give you a more accurate estimate of when you’re ovulating – and, therefore, most fertile.
These methods involve monitoring signs of fertility, including:
- cycle length – you can track the length of your cycle over 12 months to work out your fertile window (as above)
- temperature – you can take your body temperature every day. If you notice a slight rise in temperature over 3 days, this indicates your fertile window has ended
- cervix secretions – you can check your vaginal discharge for changes. If it’s wet, slippery and clear, this can mean you’re about to ovulate
- cervix changes – you can feel your cervix for changes. If it goes from being low and firm to high and soft, this can mean your fertile ’window’ has started
- hormonal changes – computerised fertility monitoring devices are available that can check your wee (urine) for changes in hormones, which can suggest you’re ovulating
Can I use fertility awareness to avoid pregnancy?
You can use fertility awareness as a method of contraception. But it takes a lot of commitment and practice to get it right.
If it’s used correctly and consistently, it’s thought to be between 91% and 99% effective at preventing pregnancy. However, with how it’s usually used in reality, it tends to be about 76% effective. This means that 24 in 100 women will get pregnant in 1 year of using this method.
If you’re considering trying natural family planning as a contraceptive, you might want to consider the pros and cons:
- it can be used by most people
- there are no side effects or health risks
- it can be inexpensive
- it can help you learn more about your body and health
- it’s typically not as effective at preventing pregnancy as other forms of contraception
- it takes time and effort to learn and needs commitment and practice
- you have to use another form of contraception – or avoid sex – during the fertile window
- fertility can be unpredictable and affected by things such as stress, illness and lifestyle
- it’s not suitable if you have irregular periods
- it can be expensive if you need to buy a monitoring device
- it doesn’t protect you from sexually transmitted infections (STIs)
When should I get medical help?
You’re more likely to get good results with natural family planning if you learn the methods from a qualified teacher. So it’s a good idea to get advice from a healthcare provider if you’re considering trying it as a method of contraception.
If you have a health condition that means getting pregnant would put you (or your baby) at risk, other, more effective forms of contraception may be more suitable. Certain health conditions make fertility-awareness methods difficult to use.
If you think you might be pregnant, or you’ve been trying to get pregnant for more than a year, speak to your doctor.
- you can get pregnant any time ovulation happens (when an egg is released) – even the first time you have sex
- you’re more likely to get pregnant – you’re more ‘fertile’ – at certain times each month
- your ‘fertile window’ happens around the time you release an egg and lasts 8 to 9 days
- fertility awareness methods, or natural family planning, can help you plan or avoid pregnancy
- natural family planning is typically one of the least effective methods of contraception