This is a blood test to check whether you are at increased chance of having a baby with a chromosomal anomaly such as Trisomy 21 (Down Syndrome) or other rarer chromosomal anomalies.
The test consists of a blood test which can be done any time between 14-20 weeks, although 14-18 is ideal. It measures four markers in your blood, and is combined with information on your weight, age, gestation, and family history to give you a low chance or increased chance result.
It is important to know that this is a screening tool. It can give you the likelihood that you might have a baby with a chromosomal anomaly – an increased chance result does not mean that your baby definitely has a condition, and a low chance result does not guarantee that they do not.
If your screening test comes back with an increased chance of chromosomal anomalies, you will be offered diagnostic testing.