Diagnostic

Prenatal diagnosis

Since prenatal diagnosis is an invasive procedure, it is offered only to pregnant women who have a high probability of having a baby with a trisomy. It consists of taking cells from the fetus, under ultrasound control, to access all of its genetic information.

It confirms whether or not there is a genetic anomaly or disease in the baby.

Prenatal diagnostic techniques

There are two techniques for prenatal diagnosis. Either can be offered to you depending on the stage of your pregnancy.

Tests	Chorionic villus biopsy	Amniocentesis
Definition	A chorionic villus biopsy, or choriocentesis, consists of taking a small sample of the chorionic cells (cells of the future placenta, the organ that nourishes the baby in the uterus) under ultrasound guidance to analyze the baby's chromosomes. Depending on the location of the placenta, a fine needle, or catheter (small hollow tube) is used either through the vagina (1) or through the abdomen (2).	Amniocentesis consists of taking, under ultrasound guidance, a small amount of amniotic fluid (the fluid that surrounds the baby) containing the fetal cells, using a fine needle inserted through the pregnant woman’s abdomen (belly), in order to analyze the chromosomes.
Time period in which the test is performed	Between the 10th and 13th week of pregnancy. Usually at the 11th or 12th week.	From the 15th week of pregnancy.
Test reliability	The result is reliable in almost 100% of cases. In 1-2% of cases, the chromosomal abnormalities detected in the placenta cells are not a reflection of the fetal chromosomes. Confirmation of results with an amniocentesis is sometimes necessary.	The result is reliable in almost 100% of cases.
Waiting period	About three days for a rapid diagnostic test.	About three days for a rapid diagnostic test.
Risk to pregnancy	Major complication: risk of miscarriage (0.33% of cases, or 1 in 300 choriocenteses). Minor complications: vaginal bleeding, uterine contractions, abdominal pain.	Major complication: risk of miscarriage (0.2% of cases, i.e. 1 in 500 and amniocenteses). Minor complications: loss of amniotic fluid, uterine contractions, abdominal pain.
Availability	In certain regions. Depends on the presence of a specialized laboratory to carry out the analysis.	In most regions. Depends on the presence of a trained specialist and ultrasound guidance.