High Levels of IRT - testing for cystic fibrosis

Has anyone been notified that their baby tested high for levels of IRT and they need to have a blood sample sent away for further testing of cystic fibrosis?

I read that IRT can be high for many reasons - one being a stressful delivery. My delivery was 28 hours and was certainly stressful, I needed 38 units of pitocin to get my baby out.

My doctor says this is really common and unless we have a family history of cystic fibrosis, the test will likely come back negative. We are going on week 3 with no results back yet.

Is anyone else going through this?