From 10 weeks gestation a small blood sample is taken from the mother’s arm and sent to a local laboratory for analysis with the IONA® test. The DNA from the mother’s blood is extracted and the test is performed on the small amount of DNA. During pregnancy, the placenta leaks cell-free DNA which circulates in the maternal bloodstream. As a result, a maternal plasma sample contains a mixture of placental and maternal circulating DNA. The IONA® test directly measures the amount of cell-free DNA and can detect small changes in the DNA ratio between the maternal and cell-free DNA when a fetal trisomy 21, 18 or 13 is present.
The IONA® Software for analysis calculates the relative amount of chromosomes 21, 18 and 13 to calculate a risk score to predict the presence of a trisomy. This figure is then combined with the mother’s age to calculate the probability of the fetus being affected.