Background. Total or cellular fibronectin (FN) determinations have been used to differentiate between normal and preeclamptic pregnants. The purpose of this study was to examine the relationship between maternal serum FN levels and the extracellular matrix molecule contents of placental tissue, such as FN, hyaluronic acid (HA) and hydroxyproline (HP) levels. Material and Methods. We obtained maternal blood samples and placental tissue samples from healthy (n = 17, controls) and preeclamptic pregnants (n = 29). We also obtained cord blood samples for FN and HA determination from the same patients. FN and HA concentrations in the placenta and maternal and cord blood were measured by and enzyme-linked immunosorbent assay and HP contents in the placenta were measured by a colorimetric assay. Results. FN levels in maternal serum, cord blood, and placenta were significantly higher in preeclamptics than in controls (p < 0.001, p < 0.001 and p < 0.05, respectively). HA concentrations in the cord blood and placenta were found to be elevated in preeclamptics (p < 0.05 and p < 0.01). Preeclamptics had significantly higher placental HP levels than controls (p < 0.001). Similar statistically significant results were obtained when the pregnant subjects classified as nulliparous and multiparous. There was no difference in ECM molecule levels between nulliporous and multiparous women in preeclamptic pregnant group. In regression analysis maternal serum FN levels were correlated with placental HA and HP levels (p < 0.01 and p < 0.01). There was a positive correlation between cord blood FN and both placental HP (p < 001) and HA levels (p < 0.01). FN levels in maternal serum, cord blood, and placenta were also negative correlated with fetal birth weight (p < 0.01, p < 0.05 and p < 0.05, respectively). Conclusion. FN in maternal serum, cord blood, and placenta is increased with elevated placental HA and HP levels, probably reflecting placental basement membrane alterations during preeclampsia.