A miscarriage is the spontaneous loss of a foetus before the twentieth week of pregnancy. Recurrent miscarriage is having usually three or more miscarriages with no successful pregnancies between them. It is regarded as a form of infertility, and may be due to chromosome abnormalities that make it impossible for the foetus to develop. Usually, these problems are unrelated to the mother or father’s genes. Other causes include Rh (blood type) incompatibility between mother and foetus, exposure to agents that can harm the foetus, such as environmental toxins, and physical problems in the mother that make it difficult for her to carry a foetus to term.