Okay. First of all you will be asked to fill in a questionnaire. 20 or so questions like, do you have a pacemaker, tattoos, clips that can't be removed etc. It's just so they know what metal could be in you and not scan you if needs be.
You will be taken through, and you get changed into a very sexy hospital gown. Remove all your jewellery, hair bands, clips and your bra. Keep on your knickers!
The tech will take you through, and position you on the couch. Depending on the machine, they will place a "coil" across your tummy; this is essentially a huge bit of plastic which helps conduct a better image with the magnets.
You will be made comfortable with cushions and wedges, and given headphones. Sometimes you get music! You will be given a call bell, which you can press if you have had enough/scared/uncomfortable.
I think you will go in feet first, so your head will be out. It's best to turn your head to the side, as you can see better and it's less scary if you don't like enclosed spaces. Keep your arms down your sides, it's much more comfortable than having them above your head.
The tech will go in the booth, turn the mic on and talk. The scan will start. When you hear the sound, that's when we are taking images. When it stops, you can wiggle, scratch your nose etc.
If your baby is moving a lot, we may give you diazapem. This might be via Injection into your vein, or orally. TBH we never did that, the baby often stayed still or if it did move, it wasn't too much of a problem or made a mess of the scan. We just repeated that frame. If the diazapem does make you drowsy and sleepy for around 2-4hrs afterwards. We use to give a 2mg dose of it which is tiny.
It usually took 30mins, and often people would fall asleep. If you're anxious, you can take someone in with you or have the healthcare to hold your hand/shoulder. Obviously you can't talk as it's so noisy.
I hope this helps!