Vintzileos A M, Egan J F, Smulian J C, Campbell W A, Guzman E R, Rodis J F
Department of Obstetrics, Gynecology, and Reproductive Sciences, Robert Wood Johnson Medical School/St. Peter's Medical Center, University of Medicine and Dentistry of New Jersey, New Brunswick, USA.
Obstet Gynecol. 1996 Jun;87(6):953-8. doi: 10.1016/0029-7844(96)00058-0.
To establish the efficacy of second-trimester fetal long-bone biometry (femur, humerus, tibia, and fibula length) in detecting trisomy 21 and to generate tables for adjusting the risk of trisomy 21 according to long-bone biometry.
Four long-bones--femur, humerus, tibia, and fibula--were measured ultrasonically in singleton fetuses before genetic amniocentesis. Fetuses with normal karyotypes were used to derive regression equations describing predicted lengths on the basis of the biparietal diameter measurement. The efficacy of each abnormally short bone, alone and in combination, was determined in 22 fetuses with trisomy 21 encountered during the study period. After the sensitivity and specificity of long-bone biometry were established, appropriate tables were generated by Bayes' theorem to adjust the risk of trisomy 21 in the second trimester depending on long-bone biometry.
Of 515 patients between 14 and 23 weeks' gestation, 493 had normal fetal karyotypes and 22 had trisomy 21. The sensitivity of an abnormal ultrasound, as defined by the presence of one or more short bones, was 63.6% and the specificity was 78.5%. According to Bayes' theorem, genetic amniocentesis may not be recommended for women less than 40 years old in the presence of normal long-bone biometry (ie, all four bones normal).
Second-trimester fetal long-bone biometry is useful in detecting trisomy 21 and may be used to adjust the a priori risk of both high- and low-risk women for trisomy 21 and, therefore, the need for genetic amniocentesis.
确定孕中期胎儿长骨（股骨、肱骨、胫骨和腓骨长度）测量在检测21三体综合征中的效能，并生成根据长骨测量调整21三体综合征风险的表格。
在进行遗传羊膜腔穿刺术前，对单胎胎儿的四根长骨（股骨、肱骨、胫骨和腓骨）进行超声测量。利用核型正常的胎儿得出基于双顶径测量的预测长度的回归方程。在研究期间遇到的22例21三体综合征胎儿中，确定每根异常短骨单独及联合检测的效能。在确定长骨测量的敏感性和特异性后，根据贝叶斯定理生成适当的表格，以根据长骨测量调整孕中期21三体综合征的风险。
在515例妊娠14至23周的患者中，493例胎儿核型正常，22例为21三体综合征。由一根或多根短骨的存在所定义的异常超声检查的敏感性为63.6%，特异性为78.5%。根据贝叶斯定理，对于长骨测量正常（即所有四根骨头均正常）的40岁以下女性，可能不建议进行遗传羊膜腔穿刺术。
孕中期胎儿长骨测量有助于检测21三体综合征，可用于调整高风险和低风险女性21三体综合征的先验风险，从而确定是否需要进行遗传羊膜腔穿刺术。
