I have the strong opinion that ultrasounds are extremely over-used in pre-natal care. With my first pregnancy I was set against any ultrasounds, but my midwife did recommend getting one at about 20 weeks to confirm healthy baby, placenta and uterus, which we did and were happy with. Of course the lovely side-benefit being that the gender can usually be determined by that time which we opted to find out. We were planning to do the same with this pregnancy.
Due to bleeding I had last Monday, I made an appointment for Monday (4 April) for an ultrasound. (On Monday the 28th I went to the hospital where I was given a super quick ultrasound to check and the baby was there and moving! Thank God!!! The diagnosis given for the bleeding was placental detachment.) The ultrasound this coming Monday is a change of plans from 20 weeks to 12 weeks... I talked to my midwife about it extensively today and again, I am so reassured that she is right in line with dp and my perspectives and she is exactly the right fit for my prenatal care and labor and birth experience. I have to say that I am also very flattered; my midwife said that I am probably the most informed woman she has ever had in her care... much of that I believe is due to my training as a doula!
My midwife asked me why we wanted an ultrasound and I said to check the placenta... and yes, to just be reassured by getting another glimpse of the baby and know that he or she is fine. We talked about potential effects on the baby. She said that studies have not been conclusive, but we do know that ultrasounds are irritating to the baby and may have negative neurological effects. Her response to my reasoning for scheduling the ultrasound for Monday was that I have thought about the potential harm vs. potential benefits and that is important. She feels it would be good to verify what the hospital doctors told me about the placental detachment. Specifically she trusts the private doctor who will do the ultrasound (and supports the midwifery model) whereas she said she cannot rely on what the public hospital doctors diagnosed and said; there are simply too many people who handled my case and thereby too much margin for error. My midwife also noted that unlike many more hippy-type midwives, she does believe in ultrasounds to help with the treatment of pregnant women when it is medically warranted and/or to know ahead of time if there is any abnormality with the baby, placenta or uterus. She also mentioned that the doctor might be able to also do a scan with a fetal monitor and with that detect any uterine contractions. If we find them, then it will be a good indication to continue with medication to relax the uterus and try to prevent the contractions.
I would never want to tell any of you what to do with your own prenatal care, but I can say that my personal skepticism of ultrasounds came from my extensive reading and training to be a doula. I would recommend that you read this article to learn more about potential risks of ultrasounds (but take it with "a grain of salt"): http://www.unhinderedliving.com/pultra.html Also if you want to read further you may want to start with books by Henci Goer (recommended on the above web link). I own "The Thinking Woman's Guide to a Better Birth" and found it enlightening with a lot of other solid research about common interventions during labor and delivery.