To evaluate the possible functional role of serum during the process of parturition, 15 serum samples were collected and analyzed for the nickel concentrations in each 3 groups(Group 1 for the period during parturition, Group 2 for the period from delivery of fetus to delivery of placenta, and Group 3 for the period after delivery of placenta) of normal, uncomplicated full term vaginal delivery and one control group composed of healthy unmarried women in 3rd decades of age. Data revealed that average serum nickel concentration of Group 2(26.6 microgram/l) and Group 1(22.2 microgram/l) were significantly higher than that of Control group(13.7 microgram/l), but Group 3's(13.8 microgram/l) was almost same as Control group's. There were significant negative correlation between age and serum nickel concentration in group 2, and a tendency of higher nickel concentration in women who have no previous experiences of pregnancy than who have previous experiences of pregnancy, although it was not significant. These result could be indicative of close causal relationship between serum nickel concentration and the entire process of parturition.