Contents
What is it for precisely?
The examination consists of taking amniotic fluid (approximately 3 or 4 teaspoons) in which the fetus bathes. This fluid is rich in fetal skin cells. They are cultured and then analyzed to study chromosomes or fetal DNA if there is any suspicion of an abnormality in the genes. Amniocentesis also makes it possible to look for bacteria, viruses or parasites (toxoplasm) in the amniotic fluid, or to measure certain substances: digestive enzymes, thyroid hormones, cholesterol… in connection with fetal disease.
In which cases is it offered?
After advice from the Pluridisciplinary Center for Prenatal Diagnosis, the mother is offered an amniocentesis if the 1st trimester screening tests show a high risk that the baby is a carrier of trisomy 21 (risk equal to or greater than 1/250) . She may be counseled when there is a probability of transmission of hereditary disease to the baby, if the mother contracted an infection during pregnancy (toxoplasmosis, rubella, CMV, etc.) or when a morphological abnormality has been identified in the pregnancy. ultrasound. It is generally practiced from the 16th week of amenorrhea (3 ½ months of pregnancy) and is possible until term.
How is it going?
You are lying on an examination table. After disinfecting your belly and placing a sterile drape, the doctor, under ultrasound control (to identify the fetus, the position of the placenta and the amniotic fluid bag), introduces a very fine needle through the abdominal wall, then the uterus. 20 cl of amniotic fluid are drawn into a syringe. Don’t worry, they renew in 1 to 2 hours! This somewhat unpleasant gesture is performed without local anesthesia and only lasts a few seconds. Then, it is advisable to lie down for the rest of the day.
“Amniocentesis is a well-established examination performed by an experienced physician under conditions of maximum asepsis.”
Does it involve a risk?
Amniocentesis is a well-honed examination performed by an experienced physician under conditions of maximum asepsis. It usually goes without a hitch. However, in 0,5% to 1% of cases, a miscarriage occurs within four weeks of the act. A risk to be put into perspective, because after twelve weeks of amenorrhea, there remains a 1% risk of miscarriage for any pregnancy. In front of any abnormal sign: pain, fever, discharge of liquid, bleeding… do not hesitate to consult quickly.
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How long do you have to wait for the results?
After the puncture, the amniotic fluid is sent to the laboratory and the cells are cultured. The result can take from a few days to several weeks depending on the case: a fortnight for the study of fetal chromosomes, a week for the search for an infection, and 24 hours for the dosage of digestive enzymes. Your doctor receives the results. In rare cases (lack of cells for analysis, for example), one may be
required to take a new amniotic fluid sample.