Primary anti-phospholipid syndrome: any role for serum complement levels in predicting pregnancy complications?

Rheumatology (Oxford). 2012 Dec;51(12):2186-90. doi: 10.1093/rheumatology/kes225. Epub 2012 Aug 25.


Objective: To evaluate the association between serum complement levels (C3 and C4) and obstetric complications.

Methods: Fifty-seven pregnancies in primary APS (PAPS) patients were compared with 49 pregnancies in patients with UCTD and SS. A group of 175 healthy pregnant women were studied to calculate a normality range for C3 and C4 during pregnancy. Such a range was applied to define hypocomplementaemia in PAPS and UCTD/SS.

Results: Both groups of patients (PAPS and UCTD/SS) showed significantly lower levels of C3 and C4 in each trimester as compared with healthy women; conversely, no significant difference was found between PAPS and UCTD/SS. Comparing PAPS pregnancies with and without complications, no difference was found in the prevalence of low C3 or low C4.

Conclusion: No association was found between hypocomplementaemia and obstetric complications in PAPS. However, both cases of pre-eclampsia were characterized by low C3 throughout pregnancy. There is evidence that the complement system is a contributor to the mechanisms of aPL-mediated damage, but its predictive role on the final pregnancy outcome does not seem to be of major impact.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Antiphospholipid Syndrome / blood
  • Antiphospholipid Syndrome / complications*
  • Case-Control Studies
  • Complement C3 / metabolism*
  • Complement C4 / metabolism*
  • Female
  • Humans
  • Pregnancy
  • Pregnancy Complications / etiology
  • Pregnancy Complications / prevention & control*
  • Pregnancy Outcome
  • Pregnancy Trimesters
  • Prenatal Diagnosis
  • Prospective Studies
  • Reference Values
  • Retrospective Studies
  • Young Adult


  • Complement C3
  • Complement C4