Testing question?

Elaine • Mom of two girls’ 👧 👧 born in Feb 2017 & August 2019!
Hi all, just wanted to get your thoughts on the following.... I am 36 years old but overall healthy person with no known prior illnesses and no family history of serious illness and currently 17wks preg. I have done 2 ultrasounds at 10wk and 16wk both came out normal. My next appt is at 20wk for another scan. My question is - is it necessary to do the genetic testing if I'm low risk and have had 2 normal ultrasounds because of my age? My doc thinks I don't need it but I'm worried :( thank you