Ultrasounds are dangerous?

Liz • Been TTC for almost 3 years. Severe male factor, pregnant with twins from donor Angel!! ❤️ p.s praying for all of u!
I'm having twins and I had one at 5, 7 and 8 weeks. Now I'm freaking out because I'm reading that autism can be caused by ultrasounds and it's more prevalent in twins. Does anyone know anything about This???