Quadruple test result and previous anencephaly

Hi ladies, just after a little advice. Last year I found out my baby had a neural tube defect - anencephaly. I'm now 17 weeks pregnant and I decided to have the quadruple test rather than the NT test as I was told it would tell me whether our baby had spina bifida. My midwife has just called and said my downs results are 1 in 840 but I have a screen positive result but this is due to having already had a baby with a neural tube defect. She said not to worry as all mums who have had a previous baby with a NTD will get that result. So just wanted to ask if anyone has had the same thing as I'm worrying.


Thank you x