So I had my 16 week check up yesterday and the nurse practitioner who performed my ultrasound asked if I wanted my blood drawn to see if my son has Spina Bifida. I agreed and thought nothing of it but then thought, what if she saw something on the U/S and wanted to confirm. She didn't seem to be worried about anything but do they test specifically for that or do they only test if they suspect he might have it? I already had the chromosome test at 12 weeks and it came back normal. Help a momma out, please?