The effect of selenium (Se) supplement on pregnancy was studied in 52 pregnant women with high risk factors of pregnancy induced hypertension (PIH). They were given natural Se dietetic liquid (100 micrograms/d) for 6-8 weeks during late pregnancy, and 48 controls were given placebo. They received similar routine prenatal care. The results revealed that Se supplement on the pregnant women prevented and decreased the incidence of PIH and gestational edema, and elevated the mother's blood Se level by 0.1008 +/- 0.091 ppm in the treated group while decreased by 0.0402 +/- 0.046 ppm in the control group (P < 0.01). The umbilical blood Se level was 0.2756 +/- 0.100 ppm in the treated group and 0.1544 +/- 0.051 ppm in the control (P < 0.01). The differences of the neonatal birth weight and the amount of postpartum hemorrhage between the two groups were not significant.