When discussing how effective contraception is, we use the terms perfect and typical use.
‘Typical use’ is what we think of as real-world use and is what we care about most. This includes all the pregnancies which happened when people were using contraception regardless of how reliably they were taking them.
‘Perfect use’ is what we see in clinical trials where researchers prompted participants 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, it becomes less dependable.
Our missed pill calculator can help work out what you need 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 minimal ‘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 unintended pregnancy during the first year of typical and perfect use of that method of contraception.
So if you followed 100 individuals who used the combined pill typically for a year, 9 would get pregnant.
This table contains estimates 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% | 0.05% |
| Male vasectomy | 0.15% | 0.10% |
| Hormonal IUD | 0.20% | 0.20% |
| Female sterilisation | 0.50% | 0.50% |
| Copper IUD | 0.80% | 0.60% |
| Copper Ballerine IUB | 0.80% | 0.60% |
| Injection | 3.00% | 0.30% |
| Natural cycles | 7.00% | 2.00% |
| Combined hormonal contraception (pill, patch, ring) | 9.00% | 0.30% |
| Progestogen-only pill (‘mini pill’) | 9.00% | <1.00% |
| Male condom | 18.00% | 2.00% |
| Diaphragm | 16.00% | 6.00% |
| Female condom | 21.00% | 5.00% |
| Fertility Awareness Method (FAM) | 22.00% | 0.40% |
| Withdrawal method (Pull out method) | 29.00% | 18.00% |
| No contraception | 85.00% | 85.00% |
A note on Fertility Awareness Methods:
- Typical use with a single fertility indicator such as the ovulation method at 1 year is around 24%
- Typical use of the symptothermal method at 1 year is 2% and with perfect use is 0.4%.
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.
- The effectiveness for the Natural Cycles app is self-reported from their website
Tags
- Trussell J. Contraceptive failure in the United States. Contraception. 2011;83(5):397-404. doi:10.1016/j.contraception.2011.01.021. Contraceptive failure rates table available here
- FSRH Clinical Guideline: Progestogen-only Pills (August 2022, Amended November 2022)
- FSRH Clinical Guideline: Combined Hormonal Contraception (January 2019, Amended November 2020)
- FSRH Clinical Guideline: Intrauterine Contraception (March 2023)
- FSRH Clinical Guideline: Male and Female Sterilisation (September 2014)
- FSRH Clinical Guideline: Progestogen-only Implant (February 2021)
- How effective is contraception? NHS website.
- Natural Cycles website
- Ballerine IUB patient information leaflet
