How well does birth control work?

The list under birth control methods goes for the real-life version – the methods are in order of how well they work based on ‘typical use’.

Some methods would come much higher up the list if we arranged it based on ‘perfect use’.

Why is 'typical' not perfect?

If you need to remember to do something regularly, like take a pill or stick on a patch, the score for ‘typical use’ is a lot lower than for ‘perfect use’. Typically, people sometimes forget!

And with things like condoms or diaphragms, people sometimes make mistakes putting them on or inserting them.

Avoiding pregnancy by avoiding sex

One way to avoid getting pregnant is simply not to have sex – or at least not have vaginal intercourse.

The ‘failure rate’ for 'perfect use' is zero! But what happens with people who aren't perfect is a different matter, and it's hard to compare with the other birth control methods. That’s why this isn’t included on the list of birth control methods in order of how well they work. The same goes for emergency contraception – the ‘morning after pill’.

What does ‘failure rate’ mean?

If a hundred women use a birth control method for a year, the number of them who get pregnant anyway is the ‘failure rate’.

For example, if a hundred women use condoms for a year each time they have sex, typically 14 of them will get pregnant. So the failure rate is 14 percent.

(That’s including all the mistakes – if they used the condoms perfectly, only three of them would probably get pregnant by accident.)

By way of comparison, if a hundred women have sex for a year without using birth control, on average 85 of them will get pregnant. So you could say using no birth control has a ‘failure rate’ of 85 percent.