You have missed the best time for Down syndrome screening, can it still be done?

Patient's question:

Has the optimal period for Down syndrome screening already been missed? Can it still be done? Week 28

Doctor's answer:

Analysis of the condition: Hello, at 28 weeks of pregnancy, you have far exceeded the time for the TSI screening. The results of this test would be inaccurate, so there is no need to do the TSI screening.
Recommendations: It is recommended that you pay attention to rest, maintain good prenatal care, and undergo regular prenatal examinations.