I am 24 and on my 28th week of pregnancy... Our little girl is diagnosed with short femur

I am really scared that our little angel has down syndrome. I am on my 27th week when we had our monthly check up and our Doctor did a pelvic ultrasound. The baby has normal abdominal and head circumference for her age, it's just that she is 3 weeks delayed in terms of her legs. And she is just 995 grams. My husband is 5'9 and I am 5'5. It's just that we have high risk pregnancy because my husband and I are somewhat blood related. Seems that our baby has so many complications, breech in presentation, cord coil and has short femur. Pls help me... I am really very worried.