L.T.
I am very sorry to hear about the loss of your babies. I pray for good health for the baby you are carrying and wish you well during your pregnancy.
I think the increase in the diagnoses of the conditions you mention are due in part to better education and screening techniques. I imagine outside influences (environment, chemicals, etc) may play a role in some of these conditions, but I know from experience that sometimes abnormalities happen without warning and without any apparent cause. As a parent that can be hard to accept.
Although I haven't done any research on it, my gut feeling is that ultrasound is safe. It is a widely used diagnostic tool that provides useful information to doctors about our babies. I think if there was a signifcant risk involved with ultrasound, it would be on every news show and added to the "danger list for pregnant women" along with radiation exposure from x-rays, mercury from eating fish, listeria from eating cold cuts, chicken pox virus, etc. I think any risk from ultrasound would be minimal. Have you talked to your doctor about your concerns?