From netdoctor.co.uk
http://www.netdoctor.co.uk/sex_relation ... epills.htm
How effective is the Pill?
It’s very effective indeed, which is why so many millions of women rely on it.
If you take it exactly as prescribed, then its effectiveness is likely to be almost 100 per cent.
Put it another way: let’s say that 100 women use the Pill for a year, and that all of them never forget to take a tablet. It’s likely that not a single one of them will get pregnant.
In contrast, if they were all relying on the condom instead, then probably about five of them would become pregnant. And if they used no contraception at all, then at least 20 of them would fall pregnant!
So the Pill is just about the most effective method of contraception there is, apart from sterilisation.