Objective  To assess the efficacy of urinary calcium output and plasma calcium for prediction of pregnancy induced hypertension (PIH).Methods:Urine samples were collected at 22?29 weeks gestation in 296 health women for the measurement of calcium,at the same time plasma calcium and creatinine were determined by automatic biochemistry analysis.All patients were followed up until delivery and classified subsequently according to the occurrence of PIH.Results:The patient in whom PIH developed later(  n  =24) had significant lower calcium of plasma and urinary (Ca    +2  ≤3.23?mmol·L    -1  ,Ca/Cr≤  0.42  ) as compared with the group which remained normal(  n  =272).Conclusions:The lower plasma calcium induced PIH.The decrease of output calcium of urine was observed before the onset of PIH.The above observation may serve as early markers for PIH.