A lil confused

Tricia • 40 Mom of 5. Josiah Tamara Joshua Jeremiah & Janessa My Lifelines. 👩🏽👦🏽👧🏽👶🏽👶🏽👧🏽 To my angel baby I love and miss you, I will never forget you 👼🏽❤️ 7/3/17
My dr has me measured at 16wks 6 days but where I had my ntd screening they have me at 17wks 5days. Which one do I follow?