We already ultrasound babies in the womb, so one would hope this has been studied.

Before ultrasound, they used to x-ray pregnant women to see the fetus. At that time, someone might have said "one would hope this has been studied"... unfortunately that practice went on for about 60 years before being stopped in the late 1950s.

Side note: kinda crazy they had medical x-rays in the 1890s. X-Ray imaging was discovered in 1985 and used clinically within 2 years.

But I do agree with your point, these days, I hope we're better about studying the potential dangers of current technologies we use.