During the first trimester of pregnancy a combined biochemical and ultrasound screening may be performed to rule out Down syndrome and neural tube defects.
First trimester maternal serum screening can check levels of free chorionic gonadotrophin fraction and the plasma protein associated with pregnancy. Sample may be obtained between 8 and 13 weeks of amenorrhea.
Between 11 and 13 weeks of gestation a transvaginal ultrasound is carried out in order to measure the nuchal translucency (NT) of the embryo.
Computational predictive mode shows the risk for diseases or conditions in a foetus or embryo before it is born, such as Down syndrome, Edwards syndrome and neural tube defects.
First Trimester Combined Test has a sensitivity (i.e. detection rate for abnormalities) of 82-87% and a false-positive rate around 5%.
