I have them often since 20 weeks due to a diabetic condition. They scan check babies head, abdomen, femur and the amniotic fluid in mine xx
I've literally just had my 28 week growth scan today and it was totally fine. I was so anxious about it as I wasn't sure what to expect, but it's actually quicker than the other scans! They're just measuring the fluid around the baby and the blood flow through the umbilical cord as well as the baby themselves. They'll let you know at the time or shortly afterwards if there are any issues, but it's usually nothing to worry about x
I had them in my last pregnancy, they are usually pretty quick and literally are just to check on the growth of baby. I loved it cus I got to see them every three weeks! 😅