Conclusions High risk fetus with trisomy 13 and 18 can be detected by routine ultrasound examination, the prenatal diagnosis rate of fetul abnormaly can be increased by prenatal ultrasound study.

• 结论 超声产前筛查能有效地检出13及18三体综合征的高风险胎儿，有助于提高胎儿染色体异常的产前诊断。