2.Etiology -(1)Heredity factors Abnomalities of chromosomesis the commonest cause of Spontaneous abortion Early abortion 50%0-60%o is caused by chromosomal abnormalities2.Etiology ◼ (1)Heredity factors Abnomalities of chromosomesis the commonest cause of Spontaneous abortion. Early abortion 50%~60% is caused by chromosomal abnormalities