AFP/Growth Ultrasounds

Has anyone had high AFP numbers and needed growth ultrasounds?? I had my genetic test at 16 weeks and there was a 1:130 chance for spina bifida. We had 2 anatomy scans and everything on the baby looked normal, but they want to monitor growth in the 3rd trimester because of the unexplained elevated AFP. I’m now 30 weeks and I have ultrasounds every appointment to measure his growth. I know the original anatomy scans came back normal, but I can’t help but worry about why they want to check his growth at every appointment. I’m hoping it’s just precaution after someone has a false positive! Anyone have a similar experience? Trying to calm my nerves :)