is it better to rely on blood test or US..

Jessica

friday i saw my ob and she told me she wanted me to run some tests like the NT but no ultrasound because her office has no one certified for it. so yesterday i went in to get blood drawn and they said ill know the gender in 2 weeks. ill be 14 weeks then. should i rely on the blood test or wait for my 20 week gender verification scan? i wamt to tell my family if its a boy or girl but dont want to rely on it if its possibly false