How Effective Is Each Contraceptive Method: Perfect Use and Typical Use

A leaflet says "over 99% effective", yet people on that method still get pregnant. Both are true: every method has two figures — pregnancies in a year when it is used exactly as directed, and pregnancies as it is actually used, with forgotten pills and condoms put on late. The less a method depends on what you do each day or each time, the smaller the gap. Only condoms also protect against sexually transmitted infections.

When to see a doctor

Right away: a late or missed period, or any chance you are pregnant, together with sudden severe pain low in the abdomen, dizziness, fainting or pain in the tip of the shoulder — possible ectopic pregnancy. You do not need a positive test first (NHS, UK). On a hormonal method: persistent severe pain in one leg, sometimes with swelling or redness, chest pain or sudden shortness of breath — possible blood clot (WHO). Call 999 in the UK, 911 in the US, 112 in the EU.

The same day: pain on one side low in the abdomen with spotting or brown watery discharge, even after a negative early pregnancy test — bleeding from an ectopic pregnancy can look like a period (NHS; in the UK, 111). Migraine with aura (flashing lights or zigzag lines before the headache) for the first time while on a combined method (NHS). Sex without contraception, a split or slipped condom, or pills missed beyond what your packet allows: get emergency contraception as soon as possible — how emergency contraception works. Possible exposure to HIV: post-exposure treatment works only if started within hours to days — STI testing: when and what.

Routinely: choosing or changing a method, starting any new medicine, planning a pregnancy.

What is happening

Pregnancies per 100 women in the first year of use (WHO Family Planning Handbook, 2022; figures largely from the United States, Trussell & Aiken, Contraceptive Technology, 2018):

Method	Perfect use	Typical use
Implant	0.1	0.1
Vasectomy	0.1	0.15
Female sterilisation	0.5	0.5
Hormonal (levonorgestrel) IUD	0.5	0.7
Copper IUD	0.6	0.8
Progestin-only injection	0.2	4
Combined pill, patch, ring	0.3	7
Progestin-only pill	0.3	7
Male condom	2	13
Withdrawal	4	20
Female condom	5	21
Diaphragm with spermicide	16	17
Spermicide	16	21
No method	85	85

Fertility awareness methods differ from one another, so they have no single figure. WHO gives: Standard Days Method 5 and 12, TwoDay Method 4 and 14, ovulation (cervical mucus) method 3 and 23, symptothermal method under 1 and 2 — the last from couples who volunteered for studies and were trained.

Three groups stand out. Implants, IUDs and sterilisation stay under 1 in 100 however they are used: once in place, there is nothing to forget. Pills, patch, ring and injections are nearly as good in perfect use, but in real life about 4–7 in 100 get pregnant a year. Condoms, withdrawal and barrier methods depend on every act, and the gap is widest.

The CDC's newer summary (US, 2023) gives the same 7 for the pill and 13 for condoms; the "9%" and "18%" in older tables are out of date. Surveys in other countries use self-report in other populations — do not mix tables.

What lowers effectiveness:

Missed pills, late patches and rings. The rule depends on the product; follow the leaflet in your pack.
Vomiting or diarrhoea. Vomiting within 2 hours of a pill — take another; severe vomiting or diarrhoea for more than 2 days counts as missed pills (WHO).
Some medicines. Rifampicin and rifabutin, several epilepsy medicines (carbamazepine, oxcarbazepine, phenytoin, primidone, topiramate, barbiturates) and St John's wort make the pill, patch, ring and progestin-only pill less effective (WHO). Ordinary antibiotics do not (CDC US MEC 2024).
Weight. Pregnancy rates with the patch may be slightly higher at 90 kg or more (WHO). For pills, WHO gives no weight data.

What to do

Choose a method that fits your life. If a daily pill is hard to remember, a method you do not have to think about closes the gap.
Add a condom with a new partner or several: other methods do not protect against infections.
Know where to get emergency contraception before you need it; keeping it at home does not make people take more risks (WHO).
Tell every doctor and pharmacist that you use hormonal contraception when a new medicine or herbal remedy starts: see never mix supplements and medications on autopilot and active ingredient vs brand name.
Where to get it. In the US, one daily progestin-only pill (Opill) has been sold without a prescription since FDA approval in 2023; other hormonal pills need a prescription. In the UK, desogestrel progestin-only pills are sold in pharmacies after a talk with the pharmacist (since 2021), and all methods are free from GPs and sexual health clinics.
Prepare questions for the appointment: bring questions to the doctor.

When this is not the case

The table is not a choice algorithm. It says nothing about side effects, bleeding patterns or what your body tolerates.
Combined methods (pill, patch, ring) are not for everyone: age 35 or over and smoking, migraine with aura, a blood clot in you or a close relative under 45, high blood pressure, heart disease (NHS; CDC US MEC 2024). Other methods remain; a doctor or nurse goes through the list with you.
After childbirth, the combined pill starts from 21 days if you are not breastfeeding and from 6 weeks if you are (NHS, UK).
Myths. Pills do not end an existing pregnancy (WHO). Fertility returns without delay after pills and the patch; after injections it returns on average several months later (WHO).
Related pages: fertility and age: what the numbers say, the menstrual cycle: what is normal, what to do when you see a scary statistic.

Sources

Checked: 24 September 2026