Chorionic villus sampling: What are chorionic villi?
Genetically, the villi originate from the fetus. Cells obtained from the chorion therefore provide reliable information about hereditary diseases, inborn errors of metabolism and chromosomal disorders of the child.
Chorionic villus sampling: What diseases can be detected?
- Trisomy 13 (Pätau syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 21 (Down syndrome)
- various hereditary metabolic diseases and other hereditary diseases such as cystic fibrosis, hemophilia or muscular dystrophy
When is a chorionic villus sampling recommended?
If the risk of prenatally diagnosable diseases or chomosome abnormalities is increased, your gynecologist will advise you to have a chorionic villus sampling. Such an increased risk exists in the following cases:
- The pregnant woman is older than 35 years.
- The pregnant woman has already given birth to a child with a hereditary disease or chromosomal disorder.
- The pregnant woman or the father of the unborn child has a genetic defect.
- Ultrasound scans detected abnormalities in the unborn baby (such as thickened nuchal fold).
When is the chorionic villus sampling performed?
A chorionic villus sampling is already possible in the 10th to 12th week of pregnancy (SSW) and thus somewhat earlier than the amniocentesis (14th to 16th SSW).
What exactly is the procedure for a chorionic villus sampling?
Transabdominal chorionic villus sampling: In an ultrasound examination, the physician first selects a suitable puncture site. There, he then inserts a thin puncture needle through the abdominal wall and carefully advances it into the placenta to remove a small amount of tissue (20 to 30 milligrams) from the chorion. The doctor carefully monitors the entire procedure via the ultrasound monitor.
Subsequently, the fetal chromosomes are extracted from the tissue sample in the laboratory and examined in more detail. If necessary, a cell culture is created for DNA analysis.
After the chorionic villus sampling
The procedure itself is experienced by most pregnant women as uncomfortable, but not very painful (similar to a blood draw). Afterwards, some women complain of some kind of cramping or a feeling of pressure in the abdominal area, but this subsides after a few hours.
When are the results of the chorionic villus sampling available?
A significant advantage of chorionic villus sampling is that the result is available within a few days at best. If, for example, a serious hereditary disease is detected in the child and the pregnant woman then decides to have an abortion, this can still take place in the first trimester. At this point, an abortion is easier for the women to cope with physically and psychologically than in the second trimester.
How safe is chorionic villus sampling?
Every procedure carries risks. The risk of miscarriage is greater with chorionic villus sampling (around one percent) than with amniocentesis (0.5 percent). This is mainly because the natural miscarriage rate is generally higher in early pregnancy than in the weeks after. Other risks include:
- Infections
- vascular injuries
- premature labor
