Hello, the ultrasound shows a 11-week gestation with 4 days of ultraso…

Hello, the ultrasound shows a 11-week gestation with 4 days of ultrasound. The thickness of the neck space (TVP) is 2.7 mm. The norm is 1.5 mm. Has anyone experienced this? I'm very worried. The sonographer says either Down syndrome or heart defect. I want to have another ultrasound by another specialist, is it harmful to do it two days in a row? Has anyone had this? How did it go?