Abstract: Objective To discuss the effective ways to prevent vitamin K deficiency bleeding early.Methods By vitamin K supplementation of pregnant women,to observe whether the vitamin K status of their newborns can be improved.The pregnant women pregnant for 36-38 weeks were divided into two groups randomly:vitamin K group and control group.In the vitamin K group,the pregnant women orally take vitamin K1 tablets(5mg/day)till labor.Cord blood samples were assayed for total osteocalcin and undercarboxylated osteocalcin and PIVA K-Ⅱ.Basing on total osteocalcin and undercarboxylated osteocalcin,the undercarboxylated osteocalcin/total osteocalcin was calculated.Results Percentages of undercarboxylated osteocalcin in vitamin K group were lower than those of control one(13.41%±11.96% to 66.66%±18.20%,P<0.001).In the control group,the PIVKA-Ⅱ rate was 26.45%,whereas,in vitamin K group,the one drop to zero(P<0.001).Conclusion Vitamin K supplementation to the pregnant women can improve the vitamin K status of their newborns.It is an alternative method for prevention of vitamin K deficiency bleeding.