大家普遍要去做的是这个: Nuchal Translucency or NT Ultrasound
This screening test is done between 11 and 14 weeks of pregnancy. Using ultrasound, your baby's length is measured to confirm your due date. Ultrasound is also used to measure the small space under the skin behind your baby's neck. This space is called the nuchal translucency(NT). The larger this space of fluid is, the greater the chance your baby has a chromosome problem. An NT ultrasound can be done only by specially trained staff.