Hello! I'm 38+5 and I did get some bad news at the 20 week scan ... but it wasn't that bad - so in case this is of use: DON'T PANIC! :)
my little boy foetus has hydronephrosis, which is basically 'urine reflux in the kidneys" - wee should be going from the kidneys to the bladder in ONE direction only, but is in fact refluxing back up. So his kidneys are a bit too full of wee. At the 20 week scan they said this could resolve itself before the birth, after the birth, or it might be something that is treated when he's a 3-6 month old baby if he's having lots of UTIs. Basically the ultrasound tech did the tour de womb, the gender reveal, and then said "I'm going to show your film to the doctor now, be back in a minute" and the doctor came back in with her and explained the condition, and how much we should worry about it. She said "Please don't worry about this yet, chances are it will resolve itself before the birth and even if it doesn't, your baby will never remember having had the condition, it's fixable." etc - she was very calming. No one WANTS anyone to 'just go and get the doctor for a moment" but they were very very good.
I went back for scans at 26 and 34 weeks, and each time they said "okay, nothing changed, some on back at xdate." and after the 34 week scan I've been going weekly so they can keep an eye on amniotic fluid levels, as if they drop suddenly I may be induced (So far nothing's changed since october and I'm hugely pregnant and desperate to get this kid out!). Now I'm talking to a pediatric urologist at the hospital where I'm delivering, and working out what the first week of his life will look like (an ultrasound on his kidneys once he's born, then some monitoring and checkups, not much else at the moment, it's a wait-and-see-if-it-fixes-itself condition, really).
My point is: This is a condition they couldn't even detect on ultrasound a few years ago. People only worked out their children had kidney problems when they were 3-6 months old and had frequent urinary tract infections. Now they can see it at 20 weeks but they still don't DO anything in most cases until the baby's a few months old (if they do anything at all). No, it's not as great as a clean bill of health but SOME of the problems they detect at the 20 week scan aren't things you can expend any useful energy on until after the birth anyway.
So I'm saying: don't worry. They might detect any number of things (which wouldn't have been knowable for our generation as babies!) and those things might not even end up being a real problem. Of course there are scary awful things that might be found, but if the technician says "I'm just off to get the doctor" please don't spiral into a panic -it might be something relatively straightforward, like I've experienced. It's not a pleasant feeling but nor is it something very awful, and people are extremely good at keeping you informed and making you feel aware.
Also: good luck and congratulations :)