is it true that getting lots of ultrasounds can cause stress for the baby?

Tamara • Mommy to my 2 beautiful baby boys, Nathan Louis💙 born August 12, 2017 and Parker Joseph May 6, 2019❤️ My whole world😍
I've heard this and wondering if this is true. This pregnancy I've only had one ultrasound (transvaginal) and one time hearing the heartbeat through the doppler. I'm not supposed to get another ultrasound until I'm 20 weeks and I'm 13 weeks now and wondering if I decide to get another done now if it's safe?