Combined screening
Trisomy 21
In trisomy 21 compared to euploid pregnancies:
- The difference in biochemical markers is greater at 11 than at 13 weeks.
- The difference in fetal NT is greater at 11 than at 13 weeks.
The performance of combined screening is better at 11 than at 13 weeks.
![](/images/Course/Course.030-003a.png)