Genetic bloodwork- praying for a false +

Hi everyone, I'm not even sure why I'm posting I just need some reassurance. I'm 27 and this is my 2nd baby. We found out from a call from my OB that my blood screen for trisomy 18 was positive. The next day he sent me to a maternal fetal specialist where I had a level 2 u/s. they said the NT measurement was perfect, but that it was too early to see other obvious deformities with T18. I am 12 weeks along. She scheduled me to come back in 4 weeks and gave me the option of a CVS now or waiting for the amino (if we decided to do further testing). My husband and I decided t wait until the 16w scan to see what it shows before continuing with any further testing. My husband and I are an absolute wreck. Has anyone experienced false positives with the genetic blood screen?