What is Amniocentesis - Purpose & Procedure

Amniocentesis Procedure: How It Works and What to Expect

Amniocentesis is a prenatal diagnostic procedure performed during pregnancy. The procedure’s objective is to get crucial information about the developing foetus. This test involves the extraction of a small sample of amniotic fluid (protective fluid surrounding the foetus in the womb). The fluid contains fetal cells and other chemicals produced by the baby that can give insights into the genetic health and development of the fetus. Read on to learn more about the amniocentesis test and everything it entails.

What is Amniocentesis?

The name ‘amniocentesis’ comes from the ‘amnion,’ which means a protective sac, and the word ‘centesis’ stands for ‘puncture’. Thus, it means to puncture the sac under ultrasound guidance.

This procedure occurs during the 15th and 20th weeks of pregnancy. It is more of a screening than a diagnostic test. This indicates that it has the potential to rule out certain chromosomal and genetic conditions with a higher degree of accuracy.

There are a few risks with amniocentesis, but recent advancements in technology and medical expertise have made the procedure a relatively safe measure.

Who Should Consider Amniocentesis?

An amniocentesis test is meant for women who have a higher risk of having a baby with a genetic condition. This includes:

Women aged 35 or older at the time of delivery
Having a previous child with a congenital defect or genetic condition
Abnormal results from an earlier screening test
Having a family history of genetic disorders
Known carriers of genetic mutations

It is vital to understand that the decision to undergo amniocentesis is personal and made after a thorough discussion with a healthcare provider or a genetic counsellor.

Purpose of Amniocentesis

There are a lot of reasons why a healthcare provider may recommend an amniocentesis test during pregnancy. Here are a few primary purposes for conducting such a test:

1. Genetic Diagnosis

One of the most common purposes for conducting an amniocentesis test is to detect a genetic or chromosomal abnormality. A few such abnormalities the procedure can help detect are Sickle cell anaemia, Down syndrome (Trisomy 21), Cystic fibrosis, Tay-Sachs disease, Muscular dystrophy, Trisomy 18 and Trisomy 13.

If any of the earlier conducted NIPS (non-invasive prenatal screening) or a first-trimester screening suggests a risk, then amniocentesis provides a definitive diagnosis.

2. Neural Tube Effects

The normal amniocentesis test results can detect neural tube defects like anencephaly and spina bifida, which indicate incomplete development of the spinal cord or brain. These conditions are not detectable through just genetic testing alone. An elevated presence of alpha-fetoprotein (AFP) in amniotic fluid indicates their presence.

3. Foetal Infections

This test can also help diagnose certain kinds of infections in the fetus. For example, it helps detect fetal infections like cytomegalovirus (CMV) or toxoplasmosis. Detection of such infections from early on leads to timely management and treatment.

4. Lung Maturity

An amniocentesis test helps detect health issues and complications like preeclampsia to assess fetal lung maturity. It happens during the third trimester of pregnancy.

5. Paternity Testing

A foetal DNA extraction from the amniotic fluid establishes paternity before birth, even though this is common and not recommended unless medically or legally necessary.

Procedure of Amniocentesis

The procedure of amniocentesis consists of two main parts: a pre-procedure preparation and the procedure itself. Here is a detailed overview of the procedure of amniocentesis:

Pre-Procedure Preparation

To begin with, a detailed ultrasound determines the position of the placenta, fetus, and pockets of amniotic fluid. This makes sure of the safest location for needle insertion. The healthcare provider then explains the procedure, risks and benefits. A consent form is signed by the patient agreeing to the treatment procedure and its methods.

Performing the Procedure

The procedure then begins with the cleaning of the abdominal area with an antiseptic solution. It reduces the risk of an infection. Depending on the gestational age, the patient needs to have either an empty or a full bladder.

By using ultrasound guidance, the doctor inserts a thin and hollow needle through the abdominal wall and into the amniotic sac. Approximately 20 ml of amniotic fluid is withdrawn. Then, the needle is removed, and the fetus is monitored shortly afterwards.

Post-Procedure

After the procedure is over, patients have to rest for the remainder of the day. There can be symptoms like spotting, cramping and fluid leakage, but that resolves quickly on its own. A doctor should immediately be informed of any signs of severe pain, fever and heavy bleeding. Then, the doctor sends a sample of amniotic fluid to a lab for analysis. Results for genetic conditions generally take 7-14 days. There are also some tests, like foetal lung maturity, where results come back within a single day.

Risks and Considerations of the Amniocentesis Test

Amniocentesis is generally safe, but unlike any other kind of invasive procedure, it carries a few risks. Here is an overview of such possible disadvantages of amniocentesis that one needs to look out for:

Miscarriage

The chances of a miscarriage after an amniocentesis test are very low, but it is still a possibility to consider. According to statistics, contemporary studies show 0.1-0.3% miscarriage risk with experienced operators.

Infection

There is a slight risk of introducing infection into the uterus when undergoing an amniocentesis procedure.

Rh Sensitisation

If the mother is Rh-negative, she will receive an injection of Rh immunoglobulin to prevent Rh incompatibility.

Needle Injury

This also happens rarely, but it is still a possibility. If the fetus moves during the amniocentesis test, then there is a risk of injury.

Final Words

The amniocentesis test is a valuable prenatal diagnostic tool which provides essential information about the development and overall health of a fetus. It offers definitive answers to many questions that a screening test only suggests. By getting answers to such valuable questions, expectant parents can make informed decisions about their pregnancy.