Goodluck Jonathan, the President of Nigeria, has just signed a measure to criminalise female genital mutilation (FGM) in one of his last acts before surrendering power to Muhammadu Buhari. It's huge news for Nigerian women – 19.9 million of them alive today are thought to have undergone the practice. The 2013 version of the bill he signed sets out a maximum punishment of four years in prison and a £650 fine for carrying out the practice that's mostly carried out on young girls between infancy and the age of 15.

FGM is normally done by a woman with no medical training, and they don't usually use anaesthetic or antiseptic treatment. They use knives, scissors, scalpels, pieces of glass or razor blades. The girls are often forcibly restrained because it hurts so much. Usually, all or part of the clitoris is removed, and often the vaginal opening is narrowed by cutting and repositioning the labia.

The effects of FGM include a high risk of infection and blood-borne viruses such as HIV, organ damage, persistent urine infections, lack of pleasure during sex, complications in pregnancy and newborn deaths. The majority of female genital mutilations are carried out in 29 countries, with all but two of these in Africa according to a 2013 study by Unicef.

Nigeria's legislation could make a huge difference to women and girls in the whole of Africa. J. Peter Pham, the director of the Africa Centre at the Atlantic Council said that the measure effectively criminalizes a significant percentage of female mutilations on the African continent.

"One cannot overestimate the impact of any decision by Nigeria," he told Buzzfeed News

However, there is a way to go yet. Campaigners don't know how exactly this law will be enforced and have said that the law needs to be backed up by projects that teach communities about the dangers of FGM.