Bright spot on his heart

Robyn • Hayden 11/25/10💙 Stormee 01/17/12❤ River 07/17/14💙 August 07/05/18💙

So I had genetic testing done and I was low risk for everything. I had an ultrasound at 16 weeks and they said they saw a bright spot on his heart. They said 5% of babies have it and it means nothing. But 15% of babies with down syndrome have it. Im just curious as to if genetic testing can come back wrong?