We studied the effect of selenium supplement on 52 pregnant women with high risk factors of pregnancy-induced hypertension (PIH) who were given the natural Se dietetic liquid (100 micrograms/day) for 6-8 weeks during late pregnancy and 48 controls. They were subjected to the same prenatal care. Se supplement on the pregnant women prevented or lowered the incidence of PIH and gestational edema. Se supplement on the pregnant women elevated the mother's blood Se level (0.1008 +/- 0.091 ppm in the treated group vs 0.0402 +/- 0.046 ppm in the control group, P < 0.01) and umbilical blood Se level (0.2756 +/- 0.1 ppm in the treated group vs 0.1544 +/- 0.051 ppm in the controls, P < 0.01). The difference of the neonatal birth weight and the amount of postpartum hemorrhage between the two groups were not significant.