Miscarriage (abortion) is defined as the expulsion of a foetus from the uterus before it is viable (i.e. is capable of life), which is said to be at a gestation of 22 - 24 weeks, or a weight of 500 grams. It may be spontaneous, or occur as a result of medical intervention. (The correct medical term is abortion, but some practitioners reserve the term miscarriage for those pregnancies which are lost spontaneously, and use abortion to describe those which are ended by intervention). It is thought that between 10 and 15 per cent of all pregnancies end in spontaneous abortion, usually between 6 and 12 weeks gestation, although it is certain that there is a much higher incidence of failed implantation, with pregnancies failing before they become established as a result of abnormalities in the formation of the early embryo. Miscarriage can occur as a result of foetal abnormality or because of maternal factors such as intercurrent illness, or abnormalities in the uterus such as fibroids. Recurrent miscarriage is defined as the loss of three consecutive pregnancies before 20 weeks gestation. It is a complication of disease of the cervix which makes it incompetent, of the anti-phospholipid syndrome (described in this section) and of recurrent chromosomal abnormalities were the mother or her partner is the carrier of a balanced translocation of genetic material (this means that a part of one chromosome is stuck onto another. When the sperm and egg fuse the resultant cell has got three copies of one chromosome, rather than two, which in many cases is incompatible with development). In a large proportion of cases of recurrent miscarriage however, there is no underlying cause found. It is felt by some to be wise to wait two full menstrual cycles before attempting to become pregnant again following a miscarriage.