Non-invasive prenatal testing which analyses the fetal DNA present in maternal blood is only one of the options for the mother to determine the risk of chromosomal disorders during pregnancy.
There are several other screenings that can be performed during this period.
In particular, a more in-depth cytogenetic investigation can be obtained by "invasive prenatal diagnosis", which can be performed on chorionic villi or amniotic fluid.
The removal of chorionic villi (placental tissue which, although separated from the fetus, contains the same DNA), or villocentesis, is carried out between the 11th and 12th week of gestation. The sampling is done through a puncture through the maternal abdomen. This carries a risk of abortion in less than 2% cases.
The cytogenetic examination is carried out by the DNA extracted from the fetal cells contained in the chorionic villi.
The sampling of the amniotic fluid or amniocentesis is performed by echo-guided trans-abdominal puncture between 16th and 18th week of pregnancy and involves a lower risk of abortion 1%. In this case, the cytogenetic examination is carried out on the fetal cells present in the amniotic fluid.
The above investigations can also provide a complete chromosomal analysis of the fetus and are recommended, in particular, to pregnant women over the age of 35 years.