The word 'infertile', for most people, means physically unable to have children. This might be due to genetics or to an illness such as cancer. An infertile couple is a couple that, for one reason or another, has been unable to have kids. That might mean a heterosexual couple where the male partner has a low sperm count, or it might be a lesbian couple (for the purposes of getting treatments like IVF, same sex treatments are referred to as 'infertile'). Infertility is a key reason why people might be considered for IVF treatment: couples who are infertile are often the only people who are accepted as patients at any IVF clinic. After all, the reasoning goes, IVF treatment should be given to people who need it most, i.e. infertile people.
Expanding the definition of infertility
Some groups have argued that the current definition of infertility is too narrow, and current infertility criteria prevent many people who need IVF and similar treatments from becoming parents. So, the World Health Organisation decided to add in another group of people to those groups who have been categorised as infertile: single people. Hitherto, single people who are otherwise fertile (i.e. who, if they had a partner of the opposite sex, would be able to have children with that partner) have been denied IVF on the grounds that they are, in principle, not infertile. However, this has left many single women, of all sexual orientations, who nevertheless would like to have children without being married or partnered, feeling left behind. Hence, it came about that women who are single for a long time, and who plan to stay that way, can have IVF treatment to have kids. Another benefit of this redefinition of infertility is that it may help to life the stigma that is currently associated with single parenthood. The World Health Organisation has clearly recognised that many people choose to become single parents - because they actively want to be, not just because things turned out that way.
Technically, now, being celibate is a 'disability'
Because of the way the law is set up around IVF, couples have historically been offered IVF on the grounds of a recognised disability that causes infertility. This new addition of single women to the group of people who can seek IVF was done by expanding this definition of disability. The WHO decided to argue that disability can also be down to 'social conditions'. I.e. if our lives are such that we are going to remain single for a long time, this is akin to the 'disability' of infertility. This opens up interesting territory for disability. Usually, disability is thought of as something to do with a person's body that makes it difficult for them to navigate the world as it is currently set up (the world being set up to favour abled people). However, now it seems, our social environments and the chances that life has dealt us can also be recognised as disabling factors.