Amniocentesis – Definition, Diagram, Procedure, and Complications

Amniocentesis is a procedure that involves the collection of amniotic fluid from the uterus for testing or treatment. The fluid surrounding and protecting a fetus during pregnancy is known as amniotic fluid. This fluid has fetal cells and different proteins.

Amniocentesis is done through genetic testing, fetal lung testing, paternity testing, and other treatments. In this article, we will learn more about Amniocentesis, the procedure and the risk factor.  

Define Amniocentesis

Amniocentesis is one of the medical procedures where a foetal sex determination test and different chromosomal abnormalities tests are carried out from the sample of the collected Amniotic Fluid surrounding the developing embryo.

1. During this procedure, a sample of amniotic fluid is taken from the amniotic sac known as amnion surrounding the unborn baby, and its DNA is examined for genetic abnormalities.
2. The amniotic fluid comprises cells derived from the foetus and the foetus’s waste products.
3. Each cell from the baby in the fluid contains its complete set of DNAs. Analyzing these cells helps doctors assess the fetus’s health and detect potential problems.
4. The entire amniocentesis appointment lasts approximately \(45\) minutes, most of which involves a detailed ultrasound examination.

Diagram

Fig: A Labeled Diagram of a Medical Procedure Called Amniocentesis

What is Amniotic Fluid?

Amniotic fluid is the fluid found in the amniotic sac that surrounds and protects a baby during pregnancy. Amniotic fluid is a clear, pale yellow fluid made by the foetus. This fluid initially contains water from the mother’s body and also contains fetal cells and various chemicals produced by the baby.

What are Invasive Techniques?

No parent wants their babies to have disorders or diseases. Right! Fortunately, it is now possible to detect hundreds of genetic mutations and chromosomal abnormalities very early in development using different Invasive Techniques.

These techniques involve the insertion of an instrument into the body. It involves amniocentesis, Chronic Villi Sampling (CVS), etc. Amniocentesis (also referred to as Amniotic Fluid Test or AFT) is a medical procedure used in prenatal diagnosis of chromosomal abnormalities and foetal infections. A small amount of amniotic fluid, which contains foetal tissues, is extracted from the amnion or amniotic sac surrounding the developing fetus. The foetal DNA is examined for genetic abnormalities. Using this process, the sex of a child can be determined, and hence, this procedure has some legal restrictions in some gender-biased countries.

Who is a Candidate for Amniocentesis?

1. Any pregnant woman who is at her due date and also who is \(40\) years of age or older.
2. Any woman whose ultrasound results indicate a potential foetal chromosomal anomaly.
3. Any woman who has a family history or whose partner has a family history of one or more incidents of chromosomal anomalies or genetic disorders with high recurrence risk.
4. It is also possible for a woman below the age of \(40\) with no history of genetic disorder to have an amniocentesis.

Amniocentesis Procedure

Amniocentesis is a prenatal medical diagnostic procedure in which a minute amount of amniotic fluid is extracted or taken and tested for chromosomal anomalies of the foetus. This procedure is generally carried out between \(15\) and \(20\) weeks of pregnancy, as doing it earlier may cause a higher risk of miscarriage in a pregnant woman.

The procedure is as follows:
1. Firstly, the amniocentesis procedure is explained to the patient, and a patient needs to sign the form by reading it thoroughly.
2. There are no specific preventive measures, but the patient has to inform the doctor regarding medical or other allergies and the details of current medications and supplements. If a patient has any history of bleeding disorders should also be informed earlier.
3. If the patient is Rh-negative, it has to be informed to ensure prophylactic immunoglobulin to be given before the procedure and thus prevent Rh sensitization and often in succeeding pregnancies.
4. Once the patient is ready for the procedure, an ultrasound examination can confirm fetal heart rate, fetal positioning, placental position, and umbilical cord location.
5. The surface disinfectant cleans the surface of the abdomen. A local anaesthetic may be injected, followed by the introduction of the ultrasound-guided amniocentesis needle through the anterior abdominal wall, the uterus, and the amniotic sac.

Fig: A Image Showing the Ultrasound Procedure

6. An ounce of amniotic fluid is taken or extracted using a syringe attached to the needle and sent for testing.
7. The needlestick site is bandaged lightly after the needle is removed, and the monitoring is done for the patient and the foetus to ensure their stability.
8. If the mother is Rh-negative, Rhogam is administered to prevent any possible Rh sensitization.
9. After monitoring is completed for an hour, the patient is sent home.
10. The fluid is tested for alpha-fetoprotein (AFP) to check some congenital defects, as well as for other metabolic disorders if indicated.

Fig: A Image Showing the Basic Procedure of Amniocentesis

Amniocentesis Complications

It is very important to be aware of the possible complications during or after amniocentesis. The complications of Amniocentesis are seen below:
Miscarriage: Miscarriage is a loss of pregnancy. There is a risk of miscarriage by performing amniocentesis, and this risk is estimated to be around \(1\) in \(100.\)
Rhesus disease is a condition where the mother is not harmed, but the fetus is. Antibodies of the mother’s blood destroy the baby’s blood cells.
1. Rhesus disease is only possible if the mother’s blood is Rh-negative and the baby’s blood is Rh-positive.
2. If this is the case, amniocentesis could trigger rhesus disease if the mother’s blood is exposed to the baby’s blood during the procedure of Amniocentesis.
Club Foot: Amniocentesis may cause a club foot in the baby. This is when the baby is born with a deformed ankle and foot. However, the chances of getting this disease are higher if the mother has amniocentesis before week \(15\) of pregnancy.
Injury from needle: The placenta may be punctured by the needle during amniocentesis. Sometimes, this is necessary to access the amniotic fluid. If this happens, the puncture wound usually heals without any more problems developing.
Infection: Infections may develop if the procedure introduces bacteria in the amniotic sac. These infections are very rare, is estimated to be less than \(1\) is \(1000\) pregnant women.

What is CVS?

Chorionic villus sampling(CVS) is another prenatal test used to detect birth defects, genetic diseases, and other problems during pregnancy. Chorionic villi are the tiny parts of the placenta formed from the fertilized egg, so they have the same genes as the baby. This sampling test is performed at \(11\) to \(14\) weeks of pregnancy by taking a small sample of placental tissue of the patient.

Amniocentesis vs CVS

Both Amniocentesis and Chorionic villus sampling are prenatal tests used to detect the foetus and other chromosomal disorders.
1. Amniocentesis is done around \(16\) to \(20\) weeks of pregnancy, and CVS is conducted around \(9\) to \(12\) weeks of pregnancy.
2. In amniocentesis, the samples are collected from the amniotic fluid, whereas, in CVS, the samples are taken from chorionic villi.
3. In the case of CVS, while collecting samples, if there is a functioning of chorionic villi, there are chances that the placenta may get deformed, or there may be chances of miscarriage. However, in amniocentesis, the pregnancies’ termination is much less than CVS.
4. Hence, doctors usually suggest amniocentesis compared to CVS.

Is Amniocentesis Illegal in India?

In India, usually killing the girl baby or killing the foetus is still present in some places. Instead of having strict rules, some people illegally try to detect the sex of the foetus.
According to India’s Pre-Conception and Pre-Natal Diagnostic Techniques Act (1994), Amniocentesis is not banned. Rather, it is regulated to find information other than the sex of the foetus. Hence, it can be used to detect hereditary disorders or any severe disorders of the foetus.

Summary

Amniocentesis is a very safe procedure that can provide helpful information about the health of a foetus. It may be offered to a woman at a higher risk of having a baby with a genetic disease. The risk of a miscarriage of amniocentesis is very rare. Amniocentesis is not compulsory, and it is up to the patient’s decision. These medical procedures are suggested only for the detection of genetic disorders and not for detecting the sex of the foetus.

FAQs

Q.1. Why amniocentesis is done?
Ans: Amniocentesis is a prenatal test conducted during pregnancy to determine the abnormalities of the foetus.

Q.2. How painful is amniocentesis?
Ans: Amniocentesis is usually not painful, but some women may feel little discomfort during the procedure.

Q.3. What is the most common reason to have amniocentesis?
Ans: The most common reason to have amniocentesis is to determine whether a foetus has any genetic disorders or a chromosomal abnormality, such as Down syndrome.

Q.4. How long should you rest after amniocentesis?
Ans: A patient who has undergone amniocentesis should rest a minimum of 24hours. In some rare cases, if the patient is a week or feels tired, then has to rest for two days.

Q.5. Do they numb you for an amniocentesis?
Ans: During the amniocentesis procedure, the doctors inject a local anaesthetic before extracting the amniotic fluid from the patient’s body.

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