Every woman has risk of having a child with a chromosomal defect. The age of the mother and the weeks of gestation are the basis on which to calculate your background risk.
Individual-specific risk for every pregnant woman and for each of her pregnancies is calculated as the age-related background risk varies depending on several parameters of fetal ultrasound between 11-13 weeks, and the levels of two hormones in maternal blood (free ß-HCG and PAPP-A). The accuracy of the test is 95%.
You will also have calculated risk of other pregnancy complications like Preterm birth, Preeclampsia and Fetal growth retardation