Health Questions and Answers

Question: What are some of the theories of the cause of preeclampsia?

Answer:

  • Immunologic response. Inadequate maternal antibody response to the fetal allograft results in vascular damage from the circulating immune complexes. This theory is supported by an increased prevalence of the disease in pregnancies with limited prior antigen exposure (young nulliparas) and in situations with increased fetal antigen (twins, molar pregnancy, hydropic pregnancies, and diabetics with large placentas). Actual measurement of immune complexes has been inconsistent.
  • Circulating toxins. Vasoconstrictive substances reportedly have been extracted from blood, amniotic fluid, and the placenta in women with preeclampsia. Symptoms have been reproduced in some but not all animal studies.
  • Endogenous vasoconstrictors. Increased sensitivity to vasopressin, epinephrine, and norepinephrine have all been reported. Loss of normal third-trimester resistance to angiotensin II has also been noted.
  • Endothelial damage. Primary endothelial damage results in a decrease in prostacyclin production (potent vasodilator) and a relative increase in thromboxane A2 (relative vasoconstrictor). Low-dose heparin or baby aspirin may play a role in prevention, but the cause of the endothelial damage and prostaglandin change is unclear.
  • Primary disseminated intravascular coagulation. Microvascular thrombin formation and deposition have been noted, producing vessel damage especially in the kidney and in the placenta.

Reference: American College of Obstetricians and Gynecologists: Diagnosis and Management of Preeclampsia and Eclampsia. ACOG Practice Bulletin No. 33. Obstet Gynecol 99:159-167, 2002

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