I had 8 scans on the big scanning equipment and one on the OB's little one. My scans varied in time - as little as a couple of minutes (OB's one) to I think nearly an hour (NT scan when a big NT measurement was found), and a similar time for the week 34 week one (for a growth check but an issue with cord blood flow was then suspected). All others were somewhere in between. He was born completely normal and as far as we can tell he has been completely unaffected by all that scanning. Try not to stress about it.

Due to a history of infertility and m/c I was often worried something was wrong. Regardless of having all those scans (none of them requested by me) I still had moments where I felt sure something was wrong. It never was. Scans will only reassure you until the next time you have doubts. I found posting in here whenever I had those doubts helped a lot.