What Are The Chances Of Down Syndrome In A Fetus With Dilated Kidneys?

Hello I m so worried. I m 30 y/o and pregnant at 32 weeks. My baby seems to have dilated kidneys which were 6mm and 8mm. Last time checked at 30 weeks they were at 6 and 5 mm so they have been shrinking. Afp was normal and everything else is normal as well according to a second level ultrasound. Worried about Down syndrome so my question is what are my chances of a ds baby?? I m pretty healthy healthy and no family hystery of ds. Please help