The WHO can say what it likes, and '4-13%' is so broad that it's statistically suspicious anyway. WHO should not be taken as an absolute authority, it's gone too far down the road of being a campaigning organisation in recent decades. It does good work but in many areas of its operations it has been captured by interest groups of which the pro-choice lobby are one. I stopped entirely trusting WHO after they disgraced themselves over second-hand smoking (which is not actually bad for you).
It's a fact that in the UK, pre-1967 when abortion was hugely liberalised, very few women were dying as a result of illegal abortion procedures. In fact death rates were almost the same as those dying from legal procedures! The data on other complications isn't available but it's a fair assumption that they were as low as the death rates.