Interaction between maternal CRP levels and diabetes on preterm delivery risk: a retrospective observation study

Preterm delivery (PTD) is a major cause of neonatal morbidity and mortality, and maternal C-reactive protein (CRP) may serve as an inflammatory marker linked to its risk, with diabetes potentially influencing this association.

To evaluate the association between maternal CRP levels and PTD risk and assess whether diabetes modifies this relationship.

This retrospective observational study included 3,089 singleton pregnancies with available CRP and covariate data from 2015 to 2022. Maternal serum CRP was measured using immuno-turbidimetry and categorized into tertiles (cut-points at 2.3 mg/L and 4.7 mg/L). Logistic regression models estimated odds ratios (ORs) for PTD, and stratified analyses evaluated interaction by diabetes status.

Among 3,089 pregnancies, 208 (6.7%) were preterm. CRP concentrations were slightly higher in PTD cases than in term births (3.5 vs. 3.3 mg/L; P = 0.042). Logistic regression showed a positive association between the highest CRP tertile and PTD in both unadjusted (β = 0.28) and adjusted models (β = 0.42). Diabetes significantly modified this association. In stratified analyses, CRP tertiles were not associated with PTD among women without diabetes (T3 vs. T1: OR = 1.16, 95% CI: 0.75-1.78), whereas among women with diabetes, being in the highest CRP tertile was associated with a substantially higher risk of PTD (OR = 2.73, 95% CI: 1.44-5.15).

Elevated maternal CRP levels were associated with higher PTD risk only among women with diabetes, suggesting that inflammation may play a more prominent etiologic role in this subgroup.