Scorza W E, Vintzileos A
Department of Obstetrics, Gynecology, and Reproductive Sciences, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, USA.
Int J Fertil Menopausal Stud. 1996 May-Jun;41(3):288-92.
In the United States, first-and second-trimester ultrasonography is most commonly used for gestational dating, detection of fetal aneuploidy, identification of early fetal intrauterine growth restriction (IUGR), and assessment for cervical incompetence. Crown-rump length (CRL) between 7 and 12 weeks is the most accurate parameter for first-trimester dating. In the second trimester, the biparietal diameter, head circumference, transverse cerebellar diameter (TCD), abdominal circumference, femur length, and other long bones, such as tibia and humerus, are useful. The TCD appears to be particularly useful because of its relative sparing in IUGR. Ultrasound can aid in the detection of fetal aneuploidy by identifying structural anomalies or abnormal fetal biometry in the first and second trimester. Numerous structural abnormalities are suggestive of aneuploidy. Cystic hygroma and nuchal translucency appear to be most significant first-trimester markers for fetal aneuploidy. Second-trimester estimated fetal weight (FFW) curves have been developed and are useful in the early detection of IUGR. Second-trimester FFW curves are useful for the detection of trisomy 18 (sensitivity 60%) but not for trisomy 21 (sensitivity 8-12%). Fetal biometry of long bones is also useful in identifying fetuses at risk for aneuploidy. Identification of a second-trimester fetus with either humerus or femur shorter than expected places the fetus at risk for aneuploidy. The sensitivity of short long bone in detection of fetal aneuploidy is approximately 30%, with false positive rates < 5%. Nuchal fold thickness > 6 mm in the second trimester is also used for identifying aneuploid fetuses. The overall sensitivity for the detection of Down's syndrome in fetuses with increased nuchal fold thickness is approximately 34% and the false positive rate is 1.5%. We have developed a model by using an ultrasound examination to adjust the mid-trimester risk for trisomy 21 by combining maternal age or triple screen risk assessment (unconjugated estriol, alpha fetoprotein, and human chorionic gonadotropin) and ultrasound. Using this model, the risk for Down's syndrome is found to be increased with identification of abnormal biometry or anomalies, or decreased with a normal genetic ultrasound examination. Another important application is the use of abdominal and transvaginal ultrasound in the second trimester in pregnancies at risk for premature cervical dilatation, premature delivery, and cervical incompetence. We have found transfundal pressure to be useful in the diagnosis of otherwise clinically inapparent premature cervical dilatation and cervical incompetence.
在美国，孕早期和孕中期超声检查最常用于确定孕周、检测胎儿非整倍体、识别早期胎儿宫内生长受限（IUGR）以及评估宫颈机能不全。孕7至12周之间的头臀长（CRL）是孕早期确定孕周最准确的参数。在孕中期，双顶径、头围、小脑横径（TCD）、腹围、股骨长度以及其他长骨（如胫骨和肱骨）都很有用。TCD似乎特别有用，因为在IUGR中它相对不受影响。超声可通过在孕早期和孕中期识别结构异常或异常胎儿生物测量来辅助检测胎儿非整倍体。许多结构异常提示非整倍体。囊性水瘤和颈部半透明带似乎是孕早期胎儿非整倍体最重要的标志物。已制定孕中期估计胎儿体重（FFW）曲线，其对早期检测IUGR很有用。孕中期FFW曲线对检测18三体（敏感性60%）有用，但对21三体（敏感性8 - 12%）无用。长骨的胎儿生物测量在识别有非整倍体风险的胎儿方面也很有用。识别出孕中期胎儿的肱骨或股骨短于预期会使胎儿有非整倍体风险。短长骨检测胎儿非整倍体的敏感性约为30%，假阳性率<5%。孕中期颈部褶皱厚度>6 mm也用于识别非整倍体胎儿。颈部褶皱厚度增加的胎儿中检测唐氏综合征的总体敏感性约为34%，假阳性率为1.5%。我们通过结合孕妇年龄或三联筛查风险评估（游离雌三醇、甲胎蛋白和人绒毛膜促性腺激素）与超声检查，开发了一种利用超声检查来调整孕中期21三体风险的模型。使用该模型，发现唐氏综合征风险会因识别出异常生物测量或异常而增加，或因基因超声检查正常而降低。另一个重要应用是在有宫颈过早扩张、早产和宫颈机能不全风险的孕中期妊娠中使用腹部超声和经阴道超声。我们发现经腹压力对诊断临床上不明显的宫颈过早扩张和宫颈机能不全很有用。
