Hi , I am 29 and due to have the combined test on Thursday. In my last pregnancy when I was 26/27 I just had the blood test for downs (the combined test wasn't around) and my risk of baby having downs was 1 in 31. He didn't have downs. Does anyone know if I am still going to be high risk or not this time? I am very anxious and fed up as this was a completely unplanned pregnancy anyway.
Downs is a genetic condition, but is down to an extra chromosome in either the egg or sperm, just a mistake when they are made it has nothing to do with your genetics. And as pp said the risk for each pregnancy is different.
I have no idea jody. Basically when the egg and sperm meet they join together making 23 complete pairs of chromosones.
Sometimes when the genetic information is randomly mixed from both egg and sperm and joined together, an extra 'bit' in included making a trio instead of a pair, in the case of Downs Syndrome the 21st set eg Trisomy 21. It's an error with the joining of the genetic information, not the information contained in either egg or sperm IYSWIM.
Just because you had a higher risk result in a previous pregnancy, but a healthy baby should not increase your risk of having a baby with Down's syndrome in future babies.
That said, it might be that you naturally have higher levels than the general population of one of the proteins they use for the risk assessment which falsely raised your risk result last time and could possibly (falsely) raise it this time, although the combined risk test is better than the blood tests alone.
The thing is that all these are only screening tests to estimate your risk and a proportion will be falsely low or high. Unless you're going to have further tests to confirm the actual genetics of the baby I think they can just cause unnecessary anxiety (as I suspect you experienced last time). I'm not convinced they explained that well enough when they offer people the test and I know my midwife seemed a little put out when I "refused" to have it as its become almost routine.
I would have thought the MW said risk could be higher based on perhaps nothing other than your age - the background risk for Downs (ie the risk based purely on maternal age and nothing else, before they have adjusted it to reflect blood / scan results) increases as you get older.