Hi Polaris. While there are risks, these risks for some women will be lower or higher depending on what they feel is acceptable for their personal situation. Below I have listed some websites that note studies that have outlined the risk of ultrasound:
https://www.mothering.com/articles/pregnancy_birth/birth_preparation/ultrasound-risks.html :
"Studies on humans exposed to ultrasound have shown possible adverse effects, including premature ovulation, preterm labor or miscarriage, low birthweight, poorer condition at birth, dyslexia, delayed speech development, and less right-handedness, a factor which in some circumstances can be a marker of damage to the developing brain. In addition, one Australian study showed that babies exposed to five or more ultrasounds were 30 percent more likely to develop intrauterine growth re tardation (IUGR)--a condition that ultrasound is often used to detect."
https://www.unhinderedliving.com/pultra.html :
"Ultrasound waves in laboratory experiments have been known to damage chromosomes, produce internal cellular heat which damages cells, re-tard the normal development of cells, and many other phenomenon."
As I said, a risk for me may not be a risk for you and vice versa.
Sometimes women just want to see their babies. I totally understand that; I was like that with my first.
PLEASE NOTE: I had to break the word re tard ation apart as apparently when you type this in a post it turns it into stars, like it's a swear word. I guess it could be used offensively as re tard to denote someone with a disability.