Amniocentesis: how, when and why it is performed
Amniocentesis is an invasive prenatal exam that is used to diagnose any fetal abnormalities due to alterations in the chromosomal heritage and more.
Amniocentesis is performed by taking a sample of the amniotic fluid that surrounds the fetus.
Amniotic fluid contains fetal cells and other substances, such as alpha-fetoprotein (AFP).
These substances can provide important information about the baby’s health before birth.
How is amniocentesis performed?
The amniotic fluid sample is extracted through a very fine needle (capillary) which is inserted into the uterus through the abdomen. No pain is felt.
The insertion of the needle takes place by ultrasound checking the procedure. In fact, the needle is eco-reflecting so that it can be seen and guided by the doctor through the ultrasound images up to the sampling point.
The collected liquid sample is subsequently sent to be analyzed in a specialized laboratory.
Several genetic tests can be performed on the liquid.
When is it recommended?
Amniocentesis is done to look for certain types of chromosomal abnormalities.
Given that it presents risks, even if minimal, for both the mother and the child, it is recommended only and exclusively when there are prerequisites for doing it, i.e.
- in the presence of ultrasound scans showing abnormalities or altered laboratory tests
- when the translucency , the Tri-Test or the Duo Test have highlighted the risk that the child is affected by chromosomal pathologies.
- in the presence of a family history of genetic diseases
- having previously had a pregnancy or a child with a congenital disease.
What can amniocentesis detect?
Amniocentesis does not detect all genetic disorders but it can be used to detect:
- chromosomal abnormalities responsible for pathologies such as Down Syndrome
- enzymatic assays of fetal cells to detect metabolic diseases in the fetus
- dosage of alpha-fetoprotein or acetylcholinesterase: these substances are present in higher than normal quantities in the amniotic fluid when the fetus has a neural tube abnormality
Since an accurate ultrasound is also performed during the amniocentesis, this can identify some defects that are not detected by the amniocentesis (such as cleft palate, clubfoot, or some cardiac anomalies).
It should be noted that there are some congenital diseases that are not detectable by amniocentesis or ultrasound scans.
Obviously with the amniocentesis you will have the certainty of the sex of the unborn child since it goes to see the karyotype and therefore the number and shape of the chromosomes.
Amniocentesis can also be performed during the third trimester of pregnancy to determine if the baby’s lungs are mature enough, in case it is necessary to deliver it earlier, or to evaluate the presence of infections in the amniotic fluid.
The exam has an accuracy of approximately 99.4%.
When is it done?
When necessary, it is scheduled between the 15th and 18th week of gestation.
What are the risks?
The risk of miscarriage exists and is above all linked to the experience of the person performing the procedure: it is however estimated between 1 in 200 and 1 in 400.
Other, but extremely rare, complications are injury to the baby or mother, infection, and premature labor.
Do I need to take any precautions after the exam?
The exam is not painful, you may feel some menstrual-like discomfort during the collection and for a few hours afterwards.
After an amniocentesis, it’s best to go home and rest for the rest of the day. No strenuous activity, no lifting weights over 20 kilos (including children) and sexual intercourse should be avoided.
In any case, the doctor will explain all the precautions to be taken and for how long.
Costs
Amniocentesis is free in the hospital for women who, regardless of age, have an increased risk of having a baby with genetic anomalies (due to family history or altered previous tests).
In private centers it usually has a cost that varies between 500 and 700 euros or more depending on the type of tests that will be done on the amniotic fluid.
Kathryn Barlow is an OB/GYN doctor, which is the medical specialty that deals with the care of women's reproductive health, including pregnancy and childbirth.
Obstetricians provide care to women during pregnancy, labor, and delivery, while gynecologists focus on the health of the female reproductive system, including the ovaries, uterus, vagina, and breasts. OB/GYN doctors are trained to provide medical and surgical care for a wide range of conditions related to women's reproductive health.