When a person is infertile it means that they are unable to have a child naturally. Infertility is define as the inability to fall pregnant or carry a pregnancy until birth after 12 months or more of unprotected sex. About 10% of people are infertile. This means that 1 in 10 people will not be able to conceive a child naturally. There are many causes of infertility some of them can be treated. As a woman gets older, her fertility declines. After menopause a woman is no longer fertile.