Amniocentesis Test

Confirmation of a pregnancy is happy news for any family. Everybody longs for a healthy child, and prenatal tests are the best way to determine if the unborn child suffers from any chromosomal anomaly. Amniocentesis is one such test that helps detect any chromosomal abnormalities in a foetus. A doctor normally recommends amniocentesis between the 15^th and 18^th week of pregnancy. The accuracy of such test is upto 99.4%.

What is Amniocentesis?

Amniocentesis (also known as an amniotic fluid test) is a procedure carried out medically, and is used in the prenatal diagnosis of the abnormalities of chromosomes and foetal infections and also for determination of the sex of the baby. Amniotic fluid surrounds and protects the baby during pregnancy. This fluid contains foetal cells and various chemicals produced by the baby. In this procedure, a small sample of the amniotic fluid which contains the foetal tissues is taken from the amniotic sac surrounding the developing foetus, and then the foetal DNA is examined for genetic abnormalities. The reason for undergoing an “amnio” (as it is colloquially referred to) is to find out whether the baby has any genetic disorder.

The procedure is conducted under local anaesthesia where the amniotic fluid is extracted through the insertion of the needle through the wall of the uterus and finally into the amniotic sac. Ultrasound guidance is used for extracting the amniotic fluid.

Although the amniocentesis genetic testing is considered a safe option, it is an invasive diagnostic test that does pose potential risks to the mother and foetus. Women of all ages should be recommended first- and second-trimester screening and diagnostic testing options.

Who Should Opt for Amniocentesis?

Any pregnant woman above the age of 35 is recommended this test, because they face an increased risk of having a child with a chromosomal abnormality. The doctor may also recommend this test if there is a family history of genetic disease or abnormality of chromosomes or if your alpha-fetoprotein levels, multiple marker screening tests or ultrasound have yielded suspicious results.

How Much Does Amniocentesis Test Cost in India?

The cost of the amniocentesis procedure depends on the doctor, lab and the tests being performed. The cost of amniocentesis in India can start from Rs. 8000 and can go up to Rs. 15,000.

Why Do People Perform an Amniocentesis Test?

If your pregnancy falls under the high-risk pregnancy category (due to any case-specific complications, or because of your age, etc.), you will be advised to take the amniocentesis test. Following insights you may get as a result of performing this test support the argument for it.

• Amniocentesis test is used for diagnosing any chromosomal or foetal problems during early pregnancy. Amnio test for Down Syndrome is such an example. Other examples include:
• Trisomy 21
• Trisomy 13
• Trisomy 18
• Other genetic disorders like cystic fibrosis, sickle cell disease or Tay-Sachs disease can also be detected. The test is used to determine the exact reason for the disorders and is not conducted to look for them.
• Neural tube defects like spina bifida and anencephaly, are determined by assessing the amount of alpha-fetoprotein in the amniotic fluid.
• The amniocentesis test can help predict foetal lung maturity. In pregnancies greater than 30 weeks, the foetal lung maturity is determined by testing the quantity of surfactant in the amniotic fluid. The production of surfactant can be correlated by several tests.
• This test can also be used to detect other problems such as:
• Infection, in which amniocentesis can detect a decreased glucose level, showing any bacteria or an abnormal count of white blood cells.
• Rh incompatibility this is a complex condition that can occur if your blood is a different type than that of your baby
• Polyhydramnios decompression

Although the amniocentesis test can help diagnose these conditions, it cannot measure the severity of the same. Amniocentesis procedure also does not detect all birth defects. It must be remembered that this test is not appropriate for everyone. In case you have an infection such as HIV/AIDS, Hepatitis B or C then this test can cause infections to be transferred to your baby at the time of the test procedure. Amniocentesis for DNA paternity testing is a very common procedure.

When to Perform Amniocentesis?

The amniocentesis test provides insights and information about your baby’s genetics. Hence the option for amniocentesis is suggested when the results of the test might have a significant impact on your pregnancy or your desire to proceed with it or not.

The test should be preferably done between the 15th and 20th week during pregnancy. Amniocentesis procedure conducted before the week 15th week can be the cause for high level complications.

You may consider the amniocentesis test if –

• The result of a prenatal test came out positive
• The screening test result has come out positive, like the first trimester or pre-natal cell free DNA screening tests are positive. In such a case you may want to opt for the amniocentesis test to verify the diagnosis
• There is a chromosomal abnormality or a defect of the neural tube from an earlier pregnancy
• Your last pregnancy was affected by Down Syndrome or neural tube defect, which is a serious condition that affects the brain or spinal cord. Then you can undergo the procedure to confirm these disorders
• You are 35 years of age or older. Babies who are born to women who are 35 years and more have a higher possibility of chromosomal abnormalities like Down syndrome.
• You have a history in your family or your spouse is a carrier of any genetic disorder
• Your ultrasound findings are abnormal. You may go in for this test to rule out any genetic condition associated with the abnormal ultrasound finding.

How to Prepare for the Amniocentesis Test?

Amniocentesis is a test conducted in the prenatal stage in which a small portion of amniotic fluid is removed from the sac around the foetus for testing under ultrasound guidance. Your doctor will brief you about the entire procedure and you can ask questions if required.

• A form has to be signed by you which will give the doctor approval to do the test. The form should be read carefully and clarified if required. Generally, there are no special limits on diet or activity before an amniocentesis.
• You will need to highlight the following to the doctor –
• Any allergies to medicines or anaesthesia.
• Highlight any medicines (prescribed by doctor or over-the-counter) and type of supplements that you are taking.
• If you have any past history of a bleeding disorder or if you are taking any blood-thinning medicines or any medicine that affects clotting of blood. These medications might need to be stopped before the amniocentesis procedure.
• Your blood type is Rh -ve. While the amniocentesis procedure is being conducted, blood cells from the mother and foetus can mix leading to Rh sensitivity and break down of the foetal red blood cells.
• Preferably this test should be conducted when the bladder is full as the uterus is in a better condition for the procedure, in case it is conducted during early pregnancy. If the test is conducted during later pregnancy the bladder should be empty.
• You will be required to follow any other instructions your doctor gives you to get ready for the test.

What is Amniocentesis Procedure?

Amniocentesis is a step by step procedure, so you will not need to stay in the hospital. You can return home after a brief observation period and will be instructed to rest for the next 24 hours.

The doctor first conducts the ultrasound to determine the baby’s location in the uterus. In amniocentesis, ultrasound uses high-frequency sound waves to create the image of the baby.

Post the ultrasound a numbing medication is applied on the belly. The ultrasound results help in the exact location for inserting the amniocentesis needle. It is inserted through the belly into the womb. A small amount of the amniotic fluid is withdrawn. This takes about 2 minutes.

The results of tests on your amniotic fluid are available within a few days.

How Does the Test Feel Like?

Amniocentesis test is not painful; however, you may feel uncomfortable during the procedure. The pain felt during the test is similar to the pain in periods. You may also feel a pressure when the needle is taken out.

What Does Amniocentesis Test Results Show?

• The most common test done on an amniocentesis sample is a chromosome test, to diagnose chromosomal abnormalities.
• To analyse the chromosomes completely, the cells from the amniotic fluid must be grown first.
• The final result is usually available within 2 weeks of the test being done.
• You may go in for a more rapid preliminary result known as the FISH test within 24-48 hours.
• If amniocentesis is performed to test for an infection or specific genetic condition your doctor will be able to tell you how long it will take to get the results. In few cases, in order to be able to interpret the results better, a chromosome test on a blood sample from the parents or further tests on the baby might also be required. In only 0.1% of the cases, a result cannot be obtained from the sample obtained and a repeat test is required.

How Accurate is an Amniocentesis Test?

The accuracy levels of an amniocentesis test are high (between 98-99%). Although the probabilities of identification are very high, the test does not measure the extremity of these birth defects.

If your test results are normal, then your baby most likely does not have any genetic or chromosomal abnormalities. Normal test results will confirm that your baby would be born with no abnormalities.

Abnormal results may mean that your baby has some genetic problem or serious birth defect. It is advisable that you discuss all test results with your doctor and partner so that you can make an informed decision about whether or not to continue your pregnancy.

Risks of Amniocentesis on Mother and Foetus

The amniocentesis procedure carries some risks as well. Some of the amniocentesis complications are as follows –

• Leakage of the amniotic fluid: There is a rare chance that the fluid leaks out through the vagina after amniocentesis procedure. In most cases, the loss of the fluid is less and stops within a week, and the pregnancy proceeds normally.
• Miscarriage: If the amniocentesis test is conducted in the 2^nd trimester then it may carry a risk of miscarriage (about 0.6% chances). As per research, the risk of miscarriage is high if amniocentesis is done before the 15^th week of pregnancy. A certain percentage of women do miscarry during the 2^nd trimester anyway. However, there is no confirmed way to determine whether miscarriage happened due to amniocentesis.
• Needle injury: There may be a chance that the baby may move an arm or leg in the path of the needle.
• Rh sensitisation. This is a rare possibility when the baby’s blood cells enter the bloodstream of the mother. If you have an Rh -ve blood group and you have not developed antibodies to Rh +ve blood, then an injection will be given to you with a Rh immune globulin after the procedure. This will prevent your body from producing any Rh antibodies that can cause damage to the red blood cells of the baby. Whether antibodies have been produced or not can be determined through a blood test.
• Uterine Infection: Uterine infection is rare post-amniocentesis procedure, but it helps to stay alert to the possibility.
• Infection transmission: If you are infected with Hepatitis B or C or HIV/AIDS it might be transferred to the baby during the amniocentesis procedure.
• Cramps after amniocentesis: You might feel slight cramps after the amniocentesis procedure.

Amniocentesis vs CVS:

Similarities:

• Amniocentesis and Chorionic villus sampling (CVS) both are prenatal diagnostic procedures used to diagnose/detect foetal genetic and chromosomal abnormalities.
• Both increase the risk of miscarriage.
• Unlike other genetic tests, amniocentesis and CVS test procedures are performed directly on the baby as opposed to the parents, which means that the knowledge about the health of the baby is more concrete. The tests performed on parents can only give approximate information of whether the child might inherit any particular genetic illnesses. Amniocentesis and CVS are actually follow-up tests that determine whether or not a child has inherited any genetic illness.

Differences:

• CVS can be performed at various stages of pregnancy, while amniocentesis can only be performed between the 15th and 20th week, CVS is usually performed between the 12th week of pregnancy (between the 10th and 14th week).
• Amniocentesis is done by inserting a needle in the womb into the amniotic sac with the guidance of ultrasound whereas CVS is done either through the abdomen or through the opening of the womb, the cervix. CVS actually takes out a small sample of the placenta.
• There is a chance of miscarriage at the rate of around 0.5-1%, in amniocentesis whereas CVS actually has a higher risk of miscarriage than amniocentesis. The chance of miscarriage in CVS is thought to be between 1 and 2%.

Benefits of Amniocentesis Test

• The amniocentesis test confirms if any chromosomal abnormality is present in the foetus that may have been detected by other tests, such as blood tests.
• It offers a specific diagnosis of chromosomal or genetic abnormality prior to the birth of the child. You can take an informed decision on whether to proceed with the pregnancy.
• Amniocentesis helps in the diagnosis of other hereditary defects depending on family history.
• It allows for the early preparation for a child with any birth defect or an early decision making as to whether to proceed with the pregnancy or not.

The amniocentesis is a diagnostic test which helps detect chromosomal abnormalities, neural tube defects and genetic disorders. Some women opt for screening and then make a decision about the diagnostic test. Others opt for the diagnostic testing right away as they may know that they are at a higher risk for a chromosomal abnormality which cannot be detected by screening.