The blood sample can be taken at any time from 10 to 13 weeks and will be used to measure two pregnancy hormones, b-HCG and PAPP-A. We ask for this in advance so that we can have the blood result and therefore give you the full report at the time of your scan appointment.
We will send you a special pack with simple instructions when you book the scan. You could have your blood taken on Level 1 of the Women's Centre at the John Radcliffe Hospital; or at your doctor's surgery if you have checked with them first. Once your blood has been taken, you should put it in the stamped addressed pack and post it the same day. Provided the blood is sent 48 hours before the scan we will usually have the hormone results in time. We advise that blood is not taken on a Thursday or Friday because of postal problems.
This takes about 20-40 minutes, although it can be longer under some circumstances. You do not need to have a full bladder. We will measure the skin thickness at the back of the baby's neck. We will also assess additional markers: the baby's nasal bone and heart rate; the blood flow across the baby's heart (tricuspid flow); and the blood flow across the liver (ductus venosus flow).