I haven't read through all of the replies to this I am sorry - just jumping in while there is a moment.

I too have been worried by the number of u/s done in the past. However, now being a mother of 4 live and 4 dead babies and a new baby growing inside I can see the benefits.

Most u/s done frequently are very quick 3mins checks - heartbeat/size. This can give a woman like me incredible relief and hope. I carried my first baby around for 2-3weeks before I knew that she was dead. This is a horrible feeling. For someone like me that has a history of this happening - the relief to see a thriving embryo/baby is immense.
I think that the Nuchal fold u/s has enormously helped women who may be at risk through their age have some peace of mind without an invasive procedure. I also think thaqt the converse is true. Ultrasound can cause enormous stress when it often isn't necessary.

It is a biggy but many people are very anti or pro. The anti are often not in the group of women who have suffered loss or have a high risk pregnancy. The pro are often the latter!

I think that much of the research is theorised - remembering that doppler also uses ultrasound technology...

Personally it has helped me - previous though to my losses I would have been quite anti - amazing what personal experience can yield!