早孕期筛查有两个目的：胎儿结构筛查及染色体异常筛查。20世纪90年代起开展结合胎儿颈后透明层及孕妇血清学指标筛查胎儿染色体异常，21三体的检出率为85%~90%，假阳性率为5%。2011年起无创产前诊断（NIPT）广泛开展，21三体的检出率达到98%~99%，假阳性率低于0.5%。NIPT筛查常见非整倍体的敏感度及特异度明显优于其他的筛查方案。但颈后透明层增厚胎儿即使染色体正常，一些结构畸形及遗传综合征的风险也会增加，尤其是心脏畸形，这些胎儿异常NIPT无法发现。在NIPT时代，早孕期超声筛查的重点在于了解胎儿有无结构畸形，如果发现颈后透明层增厚，注意了解有无合并结构畸形及遗传综合征。NIPT筛查不能取代早孕期超声筛查。

First trimester screening has two goals: fetal anatomy scanning and aneuploidy screening. In the early 1980s, the screening programs based on fetal nuchal translucency (NT) and maternal serum biochemical markers were established; the detection rate for trisomy 21 was 85%-90%, with a 5% false-positive rate. Since 2011, non-invasive prenatal testing (NIPT) has been widely carried out. The detection rate for trisomy 21 is 98%-99%, and the false positive rate is less than 0.5%. NIPT provides a test whose sensitivity and specificity in screening for the most common aneuploidies far outstrips anything available at this time. In chromosomally normal fetuses, increased NT raises suspicion for many other anomalies and syndromes, particularly congenital heart defects, which are not amenable to NIPT. In the era of NIPT, the emphasis of ultrasound screening in first trimester pregnancy is to assess fetal anatomy, including NT. If NT is increased, attention should be paid to understanding whether there are structural abnormalities and genetic syndromes. NIPT cannot replace ultrasound scanning in first trimester pregnancy.