The termination of pregnancy before the period of viability is called abortion. The period of viability is 28 weeks from the LMP. For international acceptance, the limit is brought down to 20 weeks or foetus weighing 500 gm. Miscarriage is a synonymous of abortion.
Abortion is of 2 types, i.e. - spontaneous and induced abortion.
Spontaneous abortion is again classified as- threatened abortion, inevitable abortion, complete abortion, incomplete abortion, missed abortion and septic abortion.
The induced abortion is of 2 types-
The legal one is called MTP where as the illegal one is called Criminal Abortion.
Causes of abortion-
The uterine factor or the ovo-foetal factor take a major share in spontaneous abortion; say it about 60% of total abortion. It includes chromosomal abnormalities, gross congenital malformation, degenerated chorionic villi and a blighted ovum. It occurs usually in early stage of pregnancy. Circulatory interference in the umbilical cord by knots or twists or defective placental attachment or faulty placental formation may be the cause of foetal death and expulsion.
Maternal factors contribute about 15% of total cases. It includes various infections, maternal hypoxia from acute or chronic respiratory disorders, heart failure, severe anaemia, chronic illness like hypertension, chronic nephritis, endocrinal factors like diabetes mellitus, hypothyroidism, hyperthyroidism etc. direct or indirect trauma, emotional upset or change of environment may cause impairment of uterine activity lead to abortion. In some cases cervico-uterine factors like cervical incompetence, congenital uterine malformation, uterine tumour, retroverted uterus plays a major role in abortion. Premature rupture of membrane and dietic factors like folic acid or vit-E deficiency may cause abortion. Blood ABO group and Rh incompatibility is a rare cause of foetal death.
Inspite of numerous factors, in majority cases, it is difficult to identify the actual cause. Often more than one factor is present. In about 25% of cases the aetiology is unknown till now.
Common cause of abortion according to gestational age-
1st trimester- 1.Defective germ plasm, 2.Hormonal deficiency, 3.Acute infection, 4.Trauma.
Mid trimester- 1.Cervical incompetence, 2.Uterine fibroid, 3.Uterine malformation like bicornuate uterus, septate uterus or double uterus, 4.Low implantation of placenta, 5.Twins and hydramnious.
In early weeks, the death of the ovum occurs first, followed by its expulsion. In later weeks maternal environmental factors are involved leading to expulsion of foetus which may have signs of life but is too small to survive.
To be continued.........