Wednesday, August 5, 2009

Early Pregnancy Loss: Etiology

The etiology of early pregnancy loss is varied and often controversial. More than 1 etiologic factor is often present. The most common causes of recurrent miscarriages are as follows:

  • Genetic causes
    • Mendelian disorders
    • Genetic translocations
    • Multifactorial disorders
    • Chromosomal inversions
    • Sex-chromosome aneuploidies
  • Autoimmune causes
    • Immunologic causes
    • Alloimmune causes
  • Anatomic causes
    • Uterine müllerian anomaly
      • Uterine septum (the anomaly most common associated with pregnancy loss)
      • Hemiuterus (unicornuate uterus)
      • Bicornuate uterus
    • Diethylstilbestrol-linked condition
    • Acquired defects (eg, Asherman syndrome)
    • Incompetent cervix
    • Leiomyomas
    • Uterine polyps
  • Infectious causes
  • Environmental causes
    • Smoking
    • Excessive alcohol consumption
  • Endocrine factors
    • Diabetes mellitus
    • Antithyroid antibodies
    • Luteal-phase deficiency
  • Hematologic disorders

The gestational age at the time of the SAB can provide clues about the cause. For instance, nearly 70% of SABs in the first 12 weeks are due to chromosomal anomalies. However, losses due to antiphospholipid syndrome (APS) and cervical incompetence tend to occur after the first trimester.

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