I just had a blood test today, the one that they combine with the ultrasound in a couple of weeks to give a risk assessment for downs syndrome etc.

But I was wondering what they actually measure in my blood that can indicate the chances of a problem with my baby. I would have thought that since my blood and the baby's blood aren't connected, there wouldn't be any information in mine that would be useful to tell about the baby. Can anyone tell me more detail about it? I'm not worried about it, just curious.

Thanks!