Abortion is the termination of a pregnancy before the fetus is fully developed, and in which is capable of living an independent life. When the expulsion from the womb occurs after the fetus becomes capable of independent life, which usually happens at the end of six months of pregnancy, it is technically a premature birth. There are several different types of abortion. There are also several different reasons why women get abortions (Microsoft, Encarta).
Abortions are considered to be as such when a fetus is exerted from the womb or induced. Abortions may also be spontaneous, in which it happens in less than 20 weeks of the fetus in the womb. It is estimated that some 25 percent of all human pregnancies terminate spontaneously in abortion, with three out of four abortions occurring during the first three months of pregnancy. Recurrent abortions in women decrease the probability of subsequent successful childbirths. The causes of spontaneous abortions, or miscarriages, are not clearly established. Abnormal development of the embryo or placental tissue, or both, is found in most of the cases. The abnormalities may be due to inherent faults in the germ cells. Severe vitamin deficiencies have been shown to play a role in abortions in experimental animals. Hormone deficiencies have also been found in women who are subject to recurrent abortions. Spontaneous abortions may be caused also by such maternal abnormalities as infectious diseases, systematic diseases such as diabetes. Uterine malformations, including tumors, are responsible in some instances, and extreme anxiety and other psychic disturbances may contribute to the premature expulsion of the fetus (Microsoft, Encarta).
One of the most common symptoms in threatened abortion is vaginal bleeding, with or without intermittent pain. About one-fourth of all pregnant women bleed some time during pregnancy, however, up to 50 percent of these women carry the fetus to full term.