Contraceptive effectiveness explained
What's the lowdown?
Contraceptive effectiveness can be split into perfect or typical use.
Perfect use is what is seen in clinical trials when people are reminded to use their contraceptive perfectly
Typical effectiveness reflects real-life and includes people who don’t use their contraceptive properly
The effectiveness rate is given as a percentage, sometimes it’s more useful to see the number of people who will get pregnant accidentally using the method each year
When discussing how effective contraception is, we use the terms perfect and typical use.
‘Typical use’ is what happens in the real-world and is what we care about most. This includes all the pregnancies which happened when people were using contraception, even if they weren’t using them correctly.
‘Perfect use’ is seen in clinical trials where researchers prompt users to take the contraceptives exactly how and when they should. As real-life humans, it is unlikely we will use a method 100% perfectly all the time.
Typical use probably overestimates risk for people who are reliable at using their contraceptive method. Perfect use can give false assurance of how effective a method is. In reality, the true effectiveness of contraception probably sits in between these statistics.
The more reliably you take a medication, the more likely it is to work. If you forget pills or miss the right windows for taking them, it becomes less dependable.
Our missed pill calculator can help work out how to minimise the risk of pregnancy if you have a slip-up. Remember, very few people will take a pill perfectly, but many will take it reliably.
Long-acting contraception like implants, injections and coils have very little ‘user-error’, which means that the typical and perfect use are very similar. A slight difference represents people forgetting to renew a method of contraception, and it then expires.
The table below shows the % of women experiencing an unplanned pregnancy during the first year of typical and perfect use of that method of contraception.
If you followed 100 individuals who used the combined pill typically for a year, 9 would get pregnant.
This table contains estimates on how many people will get pregnant each year based on available data. These may differ between studies or change slightly as studies are repeated or updated.
| Contraceptive method | Typical use | Perfect use |
|---|---|---|
| Implant | 0.05% (0.5 in 1000) | 0.05% (0.5 in 1000) |
| Male vasectomy | 0.15% (1.5 in 1000) | 0.1% (1 in 1000) |
| Hormonal IUD | 0.2-0.3% (2-3 in 1000) | 0.2-0.3% (2-3 in 1000) |
| Female sterilisation | 0.5% (5 in 1000) | 0.5% (5 in 1000) |
| Copper IUD | 0.8% (8 in 1000) | 0.6% (6 in 1000) |
| Copper Ballerine IUB | 0.8% (8 in 1000) | 0.6% (6 in 1000) |
| Injection | 6% (6 in 100) | 0.2% (2 in 1000) |
| Natural cycles | 7% (7 in 100) | 2% (2 in 100) |
| Combined hormonal contraception (pill, patch, ring) | 9% (9 in 100) | 0.3% (3 in 1000) |
| Progestogen-only pill (‘mini pill’) | 9% (9 in 100) | 0.3% (3 in 1000) |
| Male condom | 18% (18 in 100) | 2% (2 in 100) |
| Diaphragm | 12% (12 in 100) | 6% (6 in 100) |
| Female condom | 21% (21 in 100) | 5% (5 in 100) |
| Fertility Awareness Method (FAM) | 24% (24 in 100) | 0.4-5% (4-50 in 1000) |
| Withdrawal (pull out) | 20% (20 in 100) | 4% (4 in 100) |
| No contraception | 85% (85 in 100) | 85% (85 in 100) |
A note on the hormonal coil:
- Studies suggest that contraceptive failure during licensed use is around 0.2% for 52mg levonorgestrel containing devices (Mirena, Benilexa, Levosert) and 0.3% for the 19.5 mg (Kyleena) and 13.5 mg (Jaydess) devices.
A note on Fertility Awareness Based Methods (FABM):
- The efficacy of FABM is very difficulty to work out correctly
- Fertility indicators are different signs you can see or measurements you can take which show how fertile you are on that day. They include changes in your basal temperature, your cycle data, cervical mucus changes and ovulation tests.
- Typical use effectiveness with a single fertility indicator such as using cycle tracking only at 1 year is around 76%, meaning around 1 in 4 couples will get pregnant each year.
- However individuals using fertility awareness with a combination of fertility indicators are often more motivated and dedicated, resulting in higher effectiveness.
- The symptothermal method is a double-check method based on evaluation of cervical mucus to determine the first fertile day and evaluation of cervical mucus and temperature to determine the last fertile day
- Perfect use of the symptothermal method at 1 year has a 0.4% failure rate, meaning 4 in 1000 couples will get pregnant if they use this method perfectly all the time.
- The effectiveness for the Natural Cycles app is self-reported from their website and is currently 93% for typical use and 98% for perfect use.
A note on withdrawal (pull out) method:
- The withdrawal method relies on removing the penis all the way out of the vagina before ejaculation occurs during sex. It is not considered a reliable method of contraception on its own in the UK, but other countries can promote it. It’s best used alongside other conraceptive methods like FABM and condoms.
Dr Becky Mawson
Dr Becky is The Lowdown’s Clinical Lead. She works as a GP in Sheffield fitting and removing coils and implants. Becky also works as a researcher on improving access to sexual and reproductive healthcare.
Our medical review process
This article has been medically reviewed for factual and up to date information by a Lowdown doctor.
