Defective placentation and resultant oxidative stress are believed to be largely responsible for preeclampsia and early pregnancy toss. In experiments to test the hypothesis that these factors may also be important in complete hydatidiform mote (CHM). CHM cases were found to have significantly higher levels of mean total peroxide, mean oxidative stress index, protein carbonyls and endogenous DNA damage, and lower levels of total antioxidant potential and thiols compared with healthy pregnant patients, pointing to a role for oxidative stress in the condition. Whether this role is primary, secondary or incidental remains to be determined. (c) 2005 Elsevier Ltd. All rights reserved.