Steiger R M, Porto M, Lagrew D C, Randall R
Department of Obstetrics and Gynecology, University of California, Irvine, USA.
Ultrasound Obstet Gynecol. 1995 Jun;5(6):384-90. doi: 10.1046/j.1469-0705.1995.05060384.x.
Measurements of the fetal cisterna magna were obtained from a prospective sample of patients undergoing diagnostic obstetric ultrasound examinations. These normal measurements were then compared to a retrospective sample of ultrasound scans from fetuses with the diagnosis of trisomy 18 by amniocentesis. The fetal cisterna magna increases in size throughout pregnancy. The sample from fetuses with trisomy 18 was different and had a higher rate of small and large cisterna magnas. After the two samples were mixed, it was determined that a cut-off of 2.5 standard deviations for the fetal cisterna magna would give a sensitivity of 26.3%, specificity of 99.1%, positive predictive value of 50.0% and negative predictive value of 97.6% for trisomy 18. The probability that a fetal cisterna magna of abnormal size will predict trisomy 18 in an early second-trimester ultrasound examination with the 2.5 standard deviation cut-off was estimated at 0.019. A fetal cisterna magna that is of abnormal size appears to be of diagnostic value in identifying the fetus with trisomy 18, but its sensitivity is low.
对接受诊断性产科超声检查的患者进行前瞻性抽样，获取胎儿小脑延髓池的测量数据。然后将这些正常测量值与经羊膜穿刺术诊断为18三体胎儿的超声扫描回顾性样本进行比较。胎儿小脑延髓池在整个孕期会增大。18三体胎儿的样本则不同，小脑延髓池过小和过大的发生率更高。将两个样本混合后确定，胎儿小脑延髓池以2.5个标准差为临界值时，对18三体的敏感度为26.3%，特异度为99.1%，阳性预测值为50.0%，阴性预测值为97.6%。在孕中期早期超声检查中，以2.5个标准差为临界值时，小脑延髓池大小异常预测18三体的概率估计为0.019。小脑延髓池大小异常似乎对识别18三体胎儿具有诊断价值，但其敏感度较低。
