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® or IONA® Care tests.
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. This DNA is extracted from the mother’s blood and the test is performed on this small amount of 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 placental/fetal cell-free DNA when a fetal trisomy 21, 18 or 13 is present. IONA® Care additionally detects the small changes in the DNA ration when a Sex Chromosome Aneuploidy (SCA) or Autosomal Aneuploidy (AA) is present.
The IONA® analysis software for analysis calculates the relative amounts of the chromosomes of interest to produce a risk score in order to predict the presence of a trisomy or anueuploidy. This figure is then combined with the prior risk (by default this is the mother’s age but the result of the First Trimester Combined Test (FTCT) for Down’s, Edwards’ or Patau’s syndrome can be used instead) to calculate the probability of the fetus being affected.