Abortion (miscarriage)- Basics & Causes

Abortion (miscarriage)- Basics & Causes


Introduction

  • Abortion is the expulsion or extraction from its mother of an embryo or fetus at less than 20 weeks, or weighing 500 g or less when it is not capable of independent survival.
  • Period of viability depends on the medical facilities of a country and hence varies.
  • As per WHO-22 weeks.
  • As per ACOG-24 weeks.
  • In India: beyond 28 weeks, Fetus is l00% viable.
  • Recurrent abortion: RPL recurrent pregnancy loss. It is defined as a sequence of three or more consecutive spontaneous abortions before 20 weeks. American society for reproductive medicine (2013) defines RPL as 2 or more failed pregnancies confirmed by USG or histologically.

Incidence

  • 10-20%
  • 75% of abortions occur before the 16th week and of those, about 75% occur before the 8th week of pregnancy.

Weight of fetus

  • At 20 weeks, the weight of fetus-300 gm
  • Between 22-23 weeks-500 gm.
  • At 24 weeks, the weight of fetus-630 gms.
  • At 28 weeks, the weight of fetus-1 kg
  • 500 g of fetal development is attained approximately 22 weeks (154 days) of gestation.

Classification

  • Abortion can be broadly classified into Spontaneous & Induced abortion.
  • Spontaneous abortion can be divided into Isolated and Recurrent abortions.
  • Recurrent Abortions/ isolated abortion is further divided into:-
  1. Threatened abortion
  2. Inevitable abortion
  3. Complete abortion
  4. Incomplete abortion
  5. Missed abortion
  6. Septic abortion ( less common)
  • Induced abortion can be legal abortion (MTP) and illegal abortion.

Causes of abortion

Factors Condition causes
Fetal factors  
  • Chromosomal abnormalities (M/C cause)
  • Hydropic degeneration of villi
  • Multiple pregnancy
Maternal factors Maternal infections
  • TORCH infections
  • Malaria
  • Ureaplasma
  • Chlamydia
  • Brucella
  • Spirochaetes
  Maternal medical disorders
  • Hypertension
  • Chronic renal disease
  • Cyanotic heart disease
  • Hemoglobinopathies.
  Environmental factors
  • Alcohol
  • Smoking (leads to early pregnancy loss)
  • Caffeine
  Exposure to radiation
  • (> 5 rads) and anesthetic gases.

 

  Endocrine problems
  • Luteal phase defect (deficiency of progesterone).
  • Thyroid abnormalities – hypothyroidism.
  • Poorly controlled diabetes mellitus.
  • PCOD
  • Hyperprolactinemia
  Immunological causes
  • Antiphospholipid antibody syndrome (APLA syndrome)
  • Inherited thrombophilias
  Uterine factors like
  • Cervical incompetence
  • Mullerian anomalies (M/C associated with abortions is the septate uterus)
  • Large and multiple submucous leiomyomas.
  • Asherman syndrome
  • DES exposure in utero
  Weight of mother
  • Underweight or nutritional deficiency does not lead to abortion.
  • Obesity leads to abortion
  Others
  • Trauma
  • Subchorionic hematoma
  • Defective placentation
Paternal factors  
  • Increased paternal age is associated with increased abortion

 

 

Mnemonic To Remember Maternal Causes Of Abortion

 TIMED ‘O’ – T = Trauma (Leads to second-trimester loss)

I2 = Infections/immunological causes

M = Maternal medical diseases

E2 = Environmental factors/endocrine problem

D = Developmental/anatomical problems

O = Obesity in mother

Exam Important

  • Abortion is the expulsion or extraction of a fetus
  • As per WHO-22 weeks, As per ACOG-24 weeks, In India: beyond 28 weeks.
  • At 20 weeks, the weight of fetus-300 gm, between 22-23 weeks-500 gm.
  • At 24 weeks, the weight of fetus-630 gms, At 28 weeks, the weight of fetus-1 kg.
  • M/C cause is Chromosomal abnormalities.
  • Smoking & alcohol can cause abortion.
  • Increased paternal age is associated with increased abortion.
  • Mullerian anomalies (M/C associated with abortions is the septate uterus).
  • Trauma can lead to a second-trimester loss.
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