Google is certainly not a good thing, I had myself convinced something awful was wrong!
They'll check and note down movement and also breathing reflexes, swallowing maybe?
They measured ds3, he was not far off their estimate weight and height just a bit under. My ob just put it as getting more sneaky looks at bub as each appt for scheduled c/s and even with ob they would do a quick scan. Polyhydramios doesn't occur until usually the third trimester the fluid continues to rise.
My sisters dd was showing a slight kidney problem which she outgrew, alot of bubs can be born with one kidney slighty abnormal and it corrects itself. I think by 3 months it had disappeared when her dd went for an u/s to check how things were.