已知应用超声检查胎儿颈项透明层厚度、游离β人促绒毛膜性腺激素(hCG)和妊娠相关血浆蛋白A(PAPP-A)3项检查可有效地在妊娠期(妊娠头三个月)筛查唐氏综合征。曾有报道表明胎儿鼻骨检查可降低假阳性率同时保持较高的阳性检出率。但上述报道对于鼻骨缺失的定义为鼻骨完全缺失,或 It is known that ultrasound examination of the thickness of the transparent layer of fetal neck, free β-human chorionic gonadotropin (hCG), and pregnancy-associated plasma protein A (PAPP-A) can be effectively performed in the first trimester of pregnancy Chardonnay syndrome. It has been reported that fetal nasal examination can reduce the false positive rate while maintaining a high positive detection rate. However, the above report defines nasal bone loss as total absence of nasal bone, or