Birth control: how well does it work?
There are two ways to rate how well birth control methods work. You can say how good they are if people use them perfectly. Or you can look at what happens in real life – because people aren’t usually perfect!
Why is it ‘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.
What does ‘failure rate’ mean?
If 100 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 per cent.
(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 100 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 per cent.
100 per cent certainty
The only way to be 100 per cent sure to not get you or your partner pregnant is to not have sex and abstain.