Nipt accuracy ! Short Femur length

Hi all I had my nipt at 10 weeks (borderline minimum gestational age for nipt) and came back negative.

Had anomaly scan at 22w and I remind my baby measure behind.

Femur length is my concern. Babys femur measure very small. Doctor wasn't concerned. I am so scared because I had a previous pregnancy of Down Syndrome and I didn't make it to full term (17 weeks). I am 29 yrs old and have a healthy 5 year old.

Now I am 26 weeks still I'm worrying. Is the nipt reliable ? Has anyone had wrong nipt results.