Book dating scan
This is because blood tests for Down syndrome are not very accurate if you are having more than one baby.
Instead, you will be offered a nuchal translucency (NT) scan.
Not all units offer an early scan if all is going well in this pregnancy, though.
Ask your GP if you want the reassurance of an early scan. The scan's main purpose is to work out accurately how many weeks pregnant you are and estimate your due date.
Without an accurate due date, a blood test at what you thought was 13 weeks wouldn't be helpful if you were 16 weeks pregnant when the blood was taken. National Down's Syndrome Screening Programme for England.
Keep it with your maternity notes so your midwife and anyone else involved in your care can see it. This measurement, known as the crown rump length (CRL), is very accurate in the first trimester.If you are having a screening test for Down syndrome, you'll be offered a dating scan first.The test needs an accurate due date to be reliable, as hormones in your blood vary according to your stage of pregnancy.If you have an irregular cycle, or if you've recently been taking the contraceptive pill, working out the date from your LMP isn't a very accurate method. The scan can check that your baby has a heartbeat and is developing normally.Your baby's head, limbs, hands and feet, and some organs can be seen.