Amniocentesis: what is it and how is this diagnostic test performed?

Pregnancy and gestation are very delicate stages, since in this biological process the new organism begins to develop. That is why from a medical point of view, it is important know as much as possible about what is happening in the development of the fetus, to be able to intervene as soon as possible in the case of congenital diseases.

Amniocentesis is the procedure that doctors perform to obtain this early information. and to be able to make an early diagnosis during pregnancy. Throughout this article we will review everything you need to know about this test: what amniocentesis is, what its functions are, how it is performed, and what are the risks to be aware of.

• Related article: "The 3 phases of intrauterine or prenatal development: from the zygote to the fetus

What is an amniocentesis?

We call amniocentesis a type of prenatal test in which an early diagnosis is produced through a medical procedure of chromosomal diseases and fetal infections and that, secondarily, it also helps us to know the sex of the baby before birth.

To understand how it works, one must first know that throughout the gestation stage the fetus is surrounded by a substance called amniotic fluid, whose composition has fetal cells. From the observation of this fact, the scientific community applied to the clinical field has discovered that the amniotic fluid is capable of giving us useful information about the baby's health months before the birth occurs. birth. Amniocentesis focuses on the analysis of that substance and its components.

When performing amniocentesis, a small sample of amniotic fluid is obtained through the use of a needle that is inserted into the woman's abdomen at the same time that an ultrasound is being performed with which the process can be monitored. Secondly, the sample of amniotic fluid obtained is analyzed in the laboratory, in which context the DNA of the fetus is studied to see if there are genetic abnormalities in it.

In which cases is it done?

This prenatal test is only offered to those women who present a significant risk of genetic disease. In most cases, the main reason for performing an amniocentesis is to find out if the fetus has a chromosomal or genetic abnormality as can occur in Down syndrome. As a general rule, this diagnostic procedure It is scheduled between weeks 15 and 18 of gestation.

Thus, it is not always necessary to do it, in most cases it is only done in those pregnant women in which the baby presents some risk of developing any pathology genetics. The reason it is not done to all women is that it is about a fairly invasive test that carries a small risk of miscarriage.

Since amniocentesis is associated with certain risks, before performing it, a complete anatomical ultrasound is performed, in order to detect abnormalities in the baby. In cases where there are reasons to suspect the existence of genetic or chromosomal alterations, the amniocentesis will be performed.

Functions of this test: what is it for?

The main cases in which an amniocentesis is required include:

• A family history of birth defects.
• Abnormal results in ultrasound tests.
• Women with pregnancies or children in which there were birth or pregnancy disorders.

Unfortunately, amniocentesis falls short of detecting all possible birth defects. However, the ultrasound test that is performed at the same time can detect birth defects that not reportable on amniocentesis such as cleft lip, heart defects, cleft palate or foot baboon.

However, the risk of some birth disorders that are not detected by either of the two diagnostic tests cannot be ruled out. In general, the main diseases detected by amniocentesis are:

• Muscular dystrophy.
• Cystic fibrosis.
• sickle cell disease.
• Down's Syndrome.
• Alterations in the neural tube, as occurs in the spina bifida.
• Tay-Sachs disease and related.

Finally, the accuracy of amniocentesis is approximately 99.4%, so even if it has certain dangers is very useful in cases where there is a real suspicion of an anomaly fetal.

How do doctors do it?

After the area of ​​the abdomen where the needle will be inserted has been cleaned with an antiseptic and an anesthetic has been administered To relieve the pain of the puncture, the medical team locates the position of the fetus and placenta using a ultrasound. Giving yourself over these images, a very fine needle is inserted through the mother's abdominal wall, the wall of the uterus and the amniotic sac, trying to keep the tip away from the fetus.

A small amount of fluid is then withdrawn, about 20 ml, and this sample is sent to the laboratory where the analysis will be carried out. In this space, the fetal cells are separated from the rest of the elements present in the amniotic fluid.

These cells are cultured, fixed and stained in order to be able to see them correctly under the microscope. So, chromosomes are examined abnormalities.

As for the baby and her environment, the puncture seals and the fluid from the amniotic sac regenerate during the following 24-48 hours. The mother should go home and rest for the rest of the day, avoiding physical exercise. In a matter of a day, she can return to normal life unless the doctor indicates otherwise.

The risks

Despite the fact that safety measures in medicine have also come a long way in this area, amniocentesis always carries risks. The risk of spontaneous abortion is the most notorious, although it occurs in only 1% of cases.

The possibility of premature birth, injuries and malformations in the fetus is also an aspect to take into account.