The aim of this study was to evaluate whether pregnant women with fetal growth restriction (FGR) have higher plasma neopterin and C-reactive protein (CRP) concentrations compared with those with uncomplicated pregnancy. A total of 34 pregnant women with FGR and 62 patients with uncomplicated pregnancy were included. Neopterin and CRP levels were measured at the time of diagnosis. The primary outcome of this study was to compare the neopterin and CRP levels in pregnant women with FGR and those with uncomplicated pregnancies. The secondary outcome of our study was to evaluate the correlation between fetal birth weight and maternal neopterin levels. The serum neopterin levels were significantly elevated in pregnant women with FGR (22.71 +/- 7.70 vs 19.15 +/- 8.32). However, CRP was not elevated in pregnant women with FGR (7.47 +/- 7.59 vs 5.29 +/- 3.58). These findings support the hypothesis that pregnancy with FGR is associated with a marked increase in macrophage activation and the natural immune system.