Fetal measurements

Ashleymoore90

My blood work had came back high chance of Down syndrome around 18 weeks, I went to a high risk doctor for a more intense ultrasound and everything checked out great and put me at 95% baby didn't have downs and not to worry. Well today at my 36.6 week ultrasound to see if baby is head down baby's head is measuring 40.6 weeks, body is measuring 37 almost 38 weeks. The ultrasound tech wouldn't tell me anything just said that they would send it over to my doctor but that some babies just have big heads. Is this a cause for concern or a sign of Down syndrome? Has this happened To anyone else?