Non invasive prenatal testing
Non-invasive prenatal diagnosis differs from prenatal diagnosis, defined as invasive, as the risks attributable to the investigation are practically none. Non-invasive prenatal diagnosis includes a series of investigations ranging from ultrasound screening to the non-invasive prenatal test called NIPT. The tests included in the non-invasive prenatal diagnosis are screening tests, while those that are part of the invasive prenatal diagnosis are diagnostic tests.
The difference between diagnostic test and screening test seems subtle, but in reality it is very marked. The screening test in fact, in case of positivity, requires a diagnostic test to be confirmed. The difference is that a screening test generates a probability of disease risk. The Non-invasive Prenatal Test (NIPT) is a screening test.
Invasive prenatal diagnosis
Invasive prenatal diagnosis includes a series of investigations represented by:
- Amniocentesis: consists of the collection of amniotic fluid, on which it is possible to perform different types of analyzes depending on the indication. It is usually done around week 14-18 of gestation.
- Villocentesis: consists in the sampling of chorionic villi; it is usually performed very early (10-13 week).
- Cordocentesis: consists of taking fetal blood from the umbilical cord, usually performed around the 18-20th week of gestation.