Objectives: To evaluate changes in oxidant milieu in normotensive pregnant women (No PE) and those who developed pre-eclampsia (PE) and to define a relation between these changes and PE development. Patients & Methods: All pregnant women gave three blood samples at 12th week (S1) gestational age, start of 3rd trimester (S2) and 48-hr postpartum (S3) for spectrophotometeric estimation of serum levels of malondialdehyde (MDA) and uric acid (UA), and activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR) and catalase activity. Control group included a similar number of non-pregnant women. Blood pressures were estimated at 1st visit and monthly for diagnosis of PE. Results: 65 pregnant women developed PE; 54 had mild and 11 had severe PE; while 19 women developed early and 46 late PE. Sample S1 levels showed non-significant differences between all study participants. S2 serum MDA levels were significantly higher in pregnant women than their S1 and control levels and in PE versus No PE women. S2 serum UA levels were significantly higher in PE women than their S1, control and corresponding levels in No PE women. S2 serum SOD and GPx activity was significantly lower in PE women than their S1, control and corresponding measures in No PE women. Serum GR and catalase activities were significantly lower in S2 samples of pregnant women than their S1 and control activities with significantly lower activity in No PE women. S3 serum levels of MDA and UA were decreased and activities of antioxidant enzymes were adjusted in S3 sample than in S2 sample, but with significant difference between PE and No PE women. Statistical analysis defined serum MDA at ?13.2±0.128 µmole/L and GPx activity at ?450 U/L as risk cutoff point for PE development. Conclusion: Pregnancy is stressful condition associated with activation of oxidative stress (OS) and overproduction of oxidative products and disturbed activity of antioxidant enzymes. Exaggerated OS compromises placental functions and induces development of hypertensive manifestations. Elevated serum MDA and GPx enzyme activity could predict the progression for development of PE especially the late-onset type.