C-Reactive Protein Levels During Pregnancy
Yes, C-reactive protein (CRP) levels are elevated throughout normal pregnancy compared to non-pregnant individuals, with median values consistently higher across all trimesters. 1
Changes in CRP During Normal Pregnancy
- CRP levels are significantly higher in all trimesters of pregnancy compared to non-pregnant women, reflecting a normal physiological inflammatory response during gestation 1
- Median CRP values for pregnant women not in labor typically range from 0.7-0.9 mg/dL, with 95% of values being 1.5 mg/dL or lower 2
- During labor, CRP levels increase further, with median values reaching 1.3 mg/dL, and approximately 32% of women showing values over 1.5 mg/dL 2
Pattern of CRP Changes Throughout Pregnancy
- While CRP is consistently elevated throughout pregnancy, the pattern of change varies considerably between individual women 1
- In a longitudinal study of pregnant women:
- 52.2% showed fluctuating CRP levels throughout pregnancy
- 30.4% demonstrated progressive reductions
- 17.4% showed progressive increases 1
- No consistent trimester-to-trimester pattern of change was observed in serially sampled women not in labor 2
Physiological Basis for Elevated CRP
- Pregnancy induces a systemic inflammatory response in the mother, which includes:
- Significant increases in total white blood cell count and neutrophil counts
- Elevated circulating levels of inflammatory markers including CRP
- Increased levels of granulocyte-macrophage colony stimulating factor (GM-CSF) and lactoferrin 1
- This inflammatory state is part of normal pregnancy physiology rather than pathological 1
Clinical Implications of Elevated CRP in Pregnancy
- Elevated CRP in early pregnancy (10-14 weeks) has been associated with later development of preeclampsia and intrauterine growth restriction 3
- In a nested case-control study, women with CRP in the highest tertile had a 3.2-fold increased risk of developing preeclampsia (before adjusting for BMI) 4
- CRP levels are significantly higher in preeclamptic women compared to normotensive pregnant women in the third trimester 5
- High CRP levels in preeclamptic women negatively correlate with fetal birth weight 5
Important Considerations When Interpreting CRP in Pregnancy
- Maternal pre-pregnancy BMI strongly correlates with CRP levels, potentially confounding the relationship between CRP and pregnancy complications 4
- After adjusting for BMI, the association between elevated CRP and preeclampsia risk is attenuated but remains significant in lean women 4
- When using CRP for diagnostic purposes during pregnancy, clinicians should use pregnancy-specific reference ranges rather than non-pregnant values 2