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%).
• Polyploidy 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. ANATOMICALABNORMALITIES (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.

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

18. •THANK YOU