Is it safe to have frequent ultrasounds?

Yes: Ultrasound is very low energy, and does not appear to have any negative impact on the pregancy. We limit ultrasound to when it is medically necessary, but many women have multiple ultrasounds without apparent ill effect. The ultrasound beam is not very focused, making it hard for it to deliver a great deal of energy to the fetus.

Yes: I am not aware of any hazard from ultrasound examination. Some have wondered if some tissues are more sensitive than others, but i haven't read anything which suggests a problem.