Chin JPerinat Med,Oct.2015,V01.18,No.10 reliability assessment.the same data were collected twodifferent operators.For intra—observer reliability assessment。the data were collected analyzedtwice sameOlaIerator hour.Linearregression correlation analysis relationshipbetween CD GA.BPD,FL,HC AC.Intraclasscorrelation coe衔cient(ICC)and Bland—Altman analysis were used analysis.Results In 518f94.2%)of 550 fetuses.the CD successfullymeasured. Positively correlations between conusdistance gestationalage observed.TheCD r10.03.3)mm at>14一15 weeks(n=17)’(27.73.8)mm at>20一21 weeks ofgestation(n=18),(41.5 2.4)mm at>26一27 weeks=8),(54.73.O)mm at>32一33 weeks 0=17),and(71.92,7)mm 4l一42weeks(n=6).Linear regression correlations between CD(mm)and FL,AC,HC,BPD GAwere: CD=1.04FL(mm)一8.7l,CD=O.23AC(mm)一10.1l,CD=O.28HC(mm)一18.10,CD=0.90BPD (mm)一17.65,CD=2.34GA(weeks)一20.94(r=0,990,0.985,0.978,0.974 0.973,respectivelyallP<0.0 11.The measurement conusdistance exhibited good reproducibility between different operators (ICC=0.984,95%C/:0.972—0.99 sameoperator(ICE=0.992,95%C/:0.985—0.995)with 95%limits agreementof一1.8 3.5mm and一4.3 2.1mm.Bland—Altman analysis showed measuredvalues were within 95%confidence interval suggesting good consistency. Conclusions The distance.between conusmedullaris 1astvertebral body under ultrasound scan,iS positively correlated otherultrasonographic indicators,which ireplies anewindex fetalconus medullaris. 【Key words] Spinal cord;ultrasonograph y'prenatal;Sacrum 脊髓圆锥位于脊髓末端,由s,~S。