C-Reactive Protein (CRP) — Pregnancy Reference Values

Perinatology.com › Reference › Serum Values › C-reactive protein

C-reactive protein (serum)

CRP is an acute-phase reactant that increases with inflammation. Pregnancy itself produces a mild physiologic rise in CRP due to baseline maternal inflammatory activation.

Units Nonpregnant Adult 1st Trimester 2nd Trimester 3rd Trimester
mg/L 0.2 – 3 Not reported 0.4 – 20.3 0.4 – 8.1
Pregnancy physiology
  • CRP increases due to maternal inflammatory adaptation and innate immune activation.
  • Levels may peak mid-pregnancy and remain mildly elevated.
  • Maternal obesity significantly raises baseline levels.
  • CRP does not cross the placenta; maternal CRP does not reflect fetal inflammation.
Causes of elevated CRP
  • Physiologic pregnancy elevation
  • Infection (chorioamnionitis, pyelonephritis, pneumonia, cellulitis)
  • Preeclampsia / hypertensive disorders
  • Obesity, metabolic syndrome
  • Surgery, trauma, burns
  • Autoimmune disease (RA, SLE)
  • Smoking

CRP >10 mg/L suggests active inflammation. CRP >40–60 mg/L is commonly associated with bacterial infection.

Causes of low CRP
  • Normal healthy baseline
  • Severe hepatic dysfunction (reduced acute phase protein synthesis)
  • Immunosuppressive therapy
  • Very early infection before CRP elevation

References

  1. Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326-31.