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Spontaneous termination of pregnancy before the period of viability (POG – 20 weeks, Weight – 500gm).



15% spontaneous out of which 80% First trimester.

Common Causes of Abortion


First trimester:

  1. Genetic factors (50%) (Most common)
    1. Trisomy (60%) (most common)
    2. Triploidy
    3. Monosomy X
    4. Tetraploidy
    5. Structural rearrangements including: translocation, deletion, inversion.
  2. Endocrine disorders (luteal phase defect, thyroid abnormalities, and diabetes)
  3. Immunological disorders (autoimmune and alloimmune)
  4. Maternal medical illness including
    1. Cyanotic heart disease
    2. Hemoglobinopathies
    3. Inherited thrombophilia
  5. Trauma
  6. Maternal excessive use of alcohol, caffeine
  7. Infection ( According to ACOG (2001), infections are an uncommon cause of early abortion).
  8. Unexplained

Second trimester:

  1. Anatomic abnormalities:-
    1. Cervical incompetence (congenital or acquired) (Most common)
    2. Mullerian fusion defects (bicornuate uterus and unicornuate)
    3. Uterine synechiae, Asherman syndrome
    4. Uterine fibroid
  2. Autoimmune disorders
    - Antinuclear antibodies
    - Antiphospholipid antibodies
    - Maternal thrombophilia
  3. Rh and blood group incompatibility
  4. Maternal Medical and Endocrine abnormalities
    - Progesterone deficiency
    - Thyroid deficiency
    - Maternal diabetes
    - PCOD
    - Hypertension
  5. Maternal / Uterine infections – TORCH, malaria, ureaplasma, chlamydia, brucella, spirochaetes.
  6. Abnormal Placenta, hydromnios, twins, H.mol
  7. Unexplained

Extra Edge: Mnemonic - TIMED


        T = Trauma


        I = Infections / Immunological causes


        M = Maternal medical disease


        E = Environmental factors / Endocrine problem


        D = Developmental / Anatomical problems

  1. More than 80% of abortions occur in the first 2 weeks of pregnancy, and at least half result from chromosomal anomalies. After the first trimester, both the abortion rate and the incidence of chromosomal anomalies decrease.
  2. Trisomy 16 is the most common abnormal karyotype found in the abortus.
  3. Monosomy X (45 X), the second most frequent chromosomal abnormality (after trisomy), usually results in abortion and much less frequently in live born female infants (Turner syndrome).
  4. Advanced maternal and paternal ages do not increase the incidence of triploidy.
  5. Euploid abortion: Euploid fetuses tend to abort later in gestation than aneuploid ones. Three-fourths of aneuploid abortions occur before 8 weeks; euploid abortions peak at about 13 weeks. The incidence of euploid abortions increase dramatically after maternal age exceeds 35 years.

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