Objective: To compare macrophage activation in normal and pre-eclamptic pregnancies by determining YKL-40 concentration and chitotriosidase activity in maternal and cord serum. Methods: In this prospective case-control study samples of maternal peripheral blood and umbilical venous blood were collected from 28 pre-eclamptic and 24 normotensive pregnant women and their newborns. YKL-40 concentration and chitotriosidase activity were determined by enzyme-linked immunoassay and fluorometry, respectively. Results: Chitotriosidase activity in maternal and cord serum and YKL-40 concentration in cord serum were significantly higher in pre-eclamptic pregnancies (P 0.001), but there was no significant difference in maternal serum levels of YKL-40 between the case and control groups (P>0.05). There was a significant positive correlation between diastolic blood pressure and (1) chitotriosidase activity in both maternal and cord serum and (2) cord serum concentration of YKL-40 (r=0.61, r=0.84, and r=0.58, respectively). Conclusion: This study may be the first to demonstrate maternal and fetal macrophage activation in pre-eclampsia. (c) 2007 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved.