Why does pregnancy affect the course of rheumatoid arthritis (RA)?

Updated: May 11, 2018
  • Author: Katherine K Temprano, MD; Chief Editor: Christine Isaacs, MD  more...
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The reasons behind the ameliorating effect of pregnancy on RA activity remain unknown, but various theories have been proposed. Nonetheless, no single mechanism satisfactorily explains the observed improvement, and multiple factors are probably responsible for the decreased disease severity.

Some of the proposed theories are as follows:

  • The effect of pregnancy on cell-mediated immunity (eg, decreased cell-mediated immunity, predominance of helper T-cell 2 [TH2] cytokine profile) [6]

  • Elevated levels of anti-inflammatory cytokines, such as interleukin-1 receptor antagonist (IL-1Ra) and soluble tumor necrosis factor-alpha receptors (sTNFRs), as well as down-regulation of Th1 cytokines during pregnancy [7]

  • The effect of hormonal changes during pregnancy (eg, increased cortisol, estrogen, and progestin levels)

  • The effect of pregnancy on humoral immunity (eg, a proportional decrease in immunoglobulin G lacking terminal galactose units, an elevated serum alpha-2 pregnancy-associated globulin [PAG] level) [8, 9, 10, 11]

  • Altered neutrophil function during pregnancy (eg, decreased neutrophil respiratory burst) [12, 13]

  • The degree of HLA disparity between the mother and the fetus (the less genetically similar the mother and fetus, the more likely the RA will remit) [14]

Possible causes for flare-ups during the postpartum period include the following:

  • A decrease in the anti-inflammatory steroid levels

  • Elevated levels of prolactin (ie, proinflammatory hormone) [15]

  • Change in the neuroendocrine axis

  • Change from a TH2 to a helper T-cell 1 cytokine profile

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