Does increased peripheral C-reactive protein predate the occurrence of a short cervical length?

Shortened cervical length is an important predictor of preterm birth, though the etiology of cervical length variation has not been fully elucidated. Our objective was to evaluate the potential association between peripheral C-reactive protein (CRP), a first trimester peripheral marker of inflammation, and second trimester decreased cervical length.

Cases and controls were defined by second trimester cervical length >/<25 mm. CRP concentrations were measured in archived first trimester screen serum via commercial assay. The association between CRP and cervical length was evaluated via Wilcoxon's rank test. Both logistic and linear regressions were performed.

A total of 49 cases were matched to 98 controls. No statistically significant difference in first trimester CRP was demonstrated between cases and controls overall. Among subjects with decreased cervical lengths, however, there was a significant linear association between the degree of shortening and first trimester CRP concentrations (p = 0.022).

First trimester CRP was not associated with decreased second trimester cervical length overall. However, the degree of shortening correlated with increased first trimester CRP concentrations in patients with a short cervix. This suggests that systemic inflammation in early pregnancy may underlie variation in second trimester cervical lengths among higher risk individuals.