PATHOPHYSIOLOGY OF ABORTION PDF. NET PRESENTATION

Abortion pathophysiology ppt

1. Abortion(miscarriage) Bijay Chaudhary Public Health Inspector Officer 6th level Madhesh Institute Of Health Science

2. DEFINITION: Abortion is the expulsion or extraction from its mother of an embryo or fetus weighing 500 g or less when it is not capable of independent survival (WHO). This 500 g of fetal development is attained approximately at 22 weeks (154 days) of gestation. The expelled embryo or fetus is called abortus . INCIDENCE : The incidence of abortion is difficult to work out but probably 10–20% of all clinical pregnancies end in miscarriage and another optimistic figure of 10% are induced or deliberate. About 75% miscarriages occur before the 16th week and of these about 80% occur before the 12th week of pregnancy.

3. Classification:

4. Etiology The etiology of miscarriage is often complex and obscure. The following factors (embryonic or parental) are important: Genetic, Endocrine and metabolic, Anatomical, Infection, Immunological, Environmental, Others, Unexplained.

5. GENETIC FACTORS: Majority (50%) of early miscarriages are due to chromosomal abnormality in the conceptus. Autosomal trisomy is the commonest (50%) cytogenetic abnormality. The most common trisomy is trisomy 16 (30%). Polyploid y has been observed in about 22% of abortuses . (Polyploidy refers to the presence of three or more multiples of a haploid number of chromosome, Monosomy X (45, X) is the single most common chromosomal abnormality in miscarriages (20%). Structural chromosomal rearrangements are observed in 2–4% of abortuses . These include translocation, deletion, inversion and ring formation.

6. ENDOCRINE AND METABOLIC FACTORS (10–15%): Luteal Phase Defect (LPD) results 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 is associated with increased fetal loss. Thyroid auto-antibodies are often increased. Diabetes mellitus when poorly controlled causes increased miscarriage

7. ANATOMICAL ABNORMALITIES (3–38%) Cervico –uterine factors: These are related mostly to the second trimester abortions. (1) Cervical incompetence, either congenital or acquired is one of the commonest cause of mid trimester and recurrent abortion. (2) Congenital malformation of the uterus in the form of bicornuate or septate uterus may be responsible for mid trimester recurrent miscarriages. (3) Uterine fibroid. (4) Intrauterine adhesion.

8. Causes of fetal loss are: ( i ) Reduced intra-uterine volume, (ii) Reduced expansile property of the uterus, (iii) Reduced placental vascularity when implanted on the septum and (iv) Increased uterine irritability and contractility

9. INFECTIONS (5%)— Infections could be— ( i ) Viral: Rubella, cytomegalovirus, variola , vaccinia or HIV. (ii) Parasitic: Toxoplasma, malaria. (iii) Bacterial: Ureaplasma , chlamydia, brucella . Spirochetes hardly cause abortion before 20th week because of effective thickness of placental barrier

10. IMMUNOLOGICAL DISORDERS (5–10%) Antiphospholipid antibody syndrome (APAS)—is due to the presence of antiphospholipid antibodies. These are: lupus anticoagulant (LAC), anticardiolipin antibodies (ACAs) and b-glycoprotein 1 antibodies (b-GP1). Mechanisms of pregnancy loss in women with APAS are : (a) inhibition of trophoblast function and differentiation, (b) activation of complement pathway, (c) release of local inflammatory mediators (cytokines, interleukins) and (d) thrombosis of uteroplacental vascular bed. Ultimate pathology is fetal hypoxia.

11. MATERNAL MEDICAL ILLNESS Cyanotic heart disease, hemoglobinopathies are associated with early miscarriage. PREMATURE RUPTURE OF THE MEMBRANES inevitably leads to abortion. ENVIRONMENTAL FACTORS : Cigarette smoking—increases the risk due to formation of carboxyhemoglobin and decreased oxygen transfer to the fetus. Alcohol consumption should be avoided or minimized during pregnancy. X-irradiation and antineoplastic drugs are known to cause abortion. X-ray exposure up to 10 rad is of little risk.

12. COMMON CAUSES OF MISCARRIAGE First trimester : (1) Genetic factors (50%). (2) Endocrine disorders (LPD, thyroid abnormalities, diabetes). (3) Immunological disorders (autoimmune and alloimmune ). (4) Infection. (5) Unexplained. Second trimester : (1) Anatomic abnormalities—(a) Cervical incompetence (congenital or acquired). (b) Müllerian fusion defects ( bicornuate uterus, septate uterus). (c) Uterine synechiae . (d) Uterine fibroid. (2) Maternal medical illness. (3) Unexplained

13. MECHANISM OF MISCARRIAGE: In the early weeks, death of the ovum occurs first, followed by its expulsion. In the later weeks, maternal environmental factors are involved leading to expulsion of the fetus which may have signs of life but is too small to survive

14. Before 8 weeks : The ovum, surrounded by the villi with the decidual coverings, is expelled out intact. Sometimes, the external os fails to dilate so that the entire mass is accommodated in the dilated cervical canal and is called cervical miscarriage Between 8 weeks and 14 weeks : Expulsion of the fetus commonly occurs leaving behind the placenta and the membranes. A part of it may be partially separated with brisk hemorrhage or remains totally attached to the uterine wall Beyond 14th week : The process of expulsion is similar to that of a “mini labor”. The fetus is expelled first followed by expulsion of the placenta after a varying interval

15. THREATENED MISCARRIAGE : It is a clinical entity where the process of miscarriage has started but has not progressed to a state from which recovery is impossible INEVITABLE MISCARRIAGE It is the clinical type of abortion where the changes have progressed to a state from where continuation of pregnancy is impossible COMPLETE MISCARRIAGE : When the products of conception are expelled en masse, it is called complete miscarriage

16. INCOMPLETE MISCARRIAGE: When the entire products of conception are not expelled, instead a part of it is left inside the uterine cavity, it is called incomplete miscarriage MISSED ABORTION : When the fetus is dead and retained inside the uterus for a variable period, it is called missed miscarriage or early fetal demise. SEPTIC ABORTION : Any abortion associated with clinical evidences of infection of the uterus and its contents is called septic abortion

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