Definition of abortion:-
Abortion is the expulsion or extraction from its mother of an embryo or fetus weighting 500 gm, or less when it is not capable or independent survival. (WHO), this 500 gm, of fetal development is attained approximately at 22 weeks (154 days) or gestation. The expelled embryo or fetus is called abortus. The term miscarriage is the recommended terminology for spontaneous abortion.
Etiology of abortion:-
- Genetic factors.
- Endocrine and metabolic factors.
- Immunological disorder.
- Blood group incompatibility.
Majority (50%) of early miscarriage are due to chromosomal abnormality in the conceptus autosomal trisomy is the commonest (50%) cytogenetic abnormality. Trisomy for every chromosomes has been reported the most common trisomy is trisomy 16 (30%). Polyploidy has been observed in about 22% of abortus. (Polyploidy refers to the presence of three or more multiples of a haploid number of chromosomes. Triploid is more common then tetraploidy. Monosomy X (45X) is the single most common chromosomal abnormality in miscarriages. 20% structural chromosomal rearrangements are observed in 2.4% of abortus. These includes translocation deletion, inversion and ring formation other chromosomal abnormalities like mosaic double trisomy etc. are found in about 4% of abortions.
Endocrine and metabolic factors:-
Luteal phase defect (LPD) result in early miscarriage as implantation and placentation are not supported adequately. Deficient progesterone secretion from Corpus luteum or poor endometrial response to progesterone is the cause. Thyroid abnormalities, overt hypothyroidism or hyperthyroidism are associated with increased fetal loss. Thyroid auto antibodies are often increased Diabetes mellitus when poorly controlled cause increased miscarriage.
Are the accepted cause of late as well as early abortions. Trans placental fetal infection occur with most micro organisms and fetal losses could be caused by any. Infection could be,
1, viral– Rubella, cytomegalo,variola, vaccinia Or HIV.
2, Parasites– Toxoplasma, malaria.
3, Bacteria– Ureaplasma, chlamydia, brucella. Spirochaetes, hardly cause abortion before 20th week because of effective thickness of placental barrier.
Immunological disorder:- (5/ 10℅),
Autoimmune disease:- can cause miscarriage usually in the second trimester. These patients from antibodies against their own tissue and the placenta. These antibodies ultimately cause rejection of early pregnancy. Antibodies responsible are,
1. Anti nuclear antibodies (ANAs).
2. Anti DNA antibodies (double or single and stranded).
3. Anti phosholipid antibodies includes lupus antiocoagulant (LAC), and anticardiolipin antibodies (aCL). Spiral artery and placental intervillous thrombosis placental infection and fetal hypoxia is the ultimate Pathology to cause abortion.
Alloimmune disease:- Paternal antigens which are foreign to the mother invoke a protective blocking antibody response these blocking antibodies prevent maternal immune cells from recognising the fetus as a foreign entity. Therefore, the fetal allograft containing foreign paternal antigens are not rejected by the mother. Paternal human leukocyte antigen (HLA) sharing which the mother leads to diminished fetal-maternal immunologic interaction and ultimately fetal rejection abortion.
Antifetal antibodies:- Are deleterious to cause fetal loss as found in cases with Rh-negative women with anti-D antibodies, T-helper 1 (Th-1) cytokines (tumour necrosis factor) Interleukin (il-2), and Interferon (gamma) (IFN) are deleterious whereas T-helper 2 cytokines (IL-4, 5,6,10) are not. Down regulation of Th-1 cytokines by progesterone may improve fetal outcome. Activated NK cells damage the placental trophoblast cells to cause abortion.
Maternal medical illness:- Cyanotic heart disease, hemoglobinpathies are associated with early abortion.
Blood group incompatibility:-
Incompatible ABO group matings may be responsible for early pregnancy wastage and often recurrent but Rh incompatibility is a rare cause of death of the fetus before 28th weeks. Couple with group “A “husband and group “O” wife have got higher incidence of abortion.
Premature rupture of the membranes:-
Inevitably leads to abortion.
Paternal factors:- Sperm chromosomal anomaly (translocation) can cause miscarriage. Some women who miscarry recurrently may have normal pregnancies following marriage with a different man.
Thrombophilias:- Inherited thrombophilia, causes both early and late miscarriage due to intravascular coagulation. Protein C resistance (factor V Leiden mutation) is the most common cause. Other conditions are protein C deficiency and hyperhomocysteinemia.
- Ciggarette smoking.
- Contraceptive agents.
- Drugs, chemicals, noxious agents.
Common causes of miscarriage:-
- Genetic factors (50℅).
- Endocrine disorders ( LPD, thyroid abnormalities diabetes)
- Immunological disorders (autoimmune and Alloimmune)
- Anatomic abnormalities (a), Cervical incompetence (congenital aur acquired). (b), Mullerian fusion defects (Bicornuate, uterus, septate, uterus). Uterine synechiae. (d) uterine fibroid.
- Maternal medical illness.
Mechanism of miscarriage:-
In the early weeks, death of the ovum occurs first, followed by it’s expulsion. In the later weeks, maternal environmental factors are involved leading to expulsion of the fetus which may have sign of life but is to small to survive.
Before 8 weeks, The ovum, surrounded by the villi with the decidual coverings, is expelled out intact, sometimes, the external so fails to dilate so that the entire mass is accommodate in the dilated cervical canal and is called cervical miscarriage.
8-14 weeks, Expulsion of the fetus commonly occurs leaving behind the placenta and the membranes. A part of it may be partially separate with brisk Haemorrhage Or remains totally attached to the uterine wall.
Behind 14 th weeks:- The process of expulsion is similar to that of a “mini labour. The fetus is expelled first followed by expulsion of the placenta after a varying interval.
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By GS India Nursing…………….!!