Amniocentesis

The fetus grows in the uterus inside an amniotic sac that contains amniotic fluid in which cells that contain fetal chromosomes are discharged. During an amniocentesis, a small sample of this fluid (the fluid renews itself within several hours) is extracted and sent to a genetic laboratory for diagnosis of chromosomal disorders, including down syndrome, and depending on a clinical need or recommendation, to detect the presence of genetic diseases in the fetus.

Since the amniocentesis is a form of direct testing of the fetus, it is considered a diagnostic test performed during pregnancy.

Objectives of the test

• A test of the fetal chromosomes: normally, a fetus has 46 chromosomes that are divided into pairs: 22 pairs of autosomal chromosomes (chromosomes that are not sex chromosomes) and 2 sex chromosomes - XX for female and XY for male. Mutations in several chromosomes can cause various chromosomal disorders. The test is performed with a molecular method that examines fetal DNA using the Genetic Chip Analysis (also known as CMA). It can facilitate a diagnosis of Down Syndrome (characterized by an extra copy of chromosome 21) and can detect other mutations attributed to extra or missing chromosomal segments.
• Diagnosis of a known hereditary disease in the family: if there is an increased risk of a certain disease, fetal cells will be tested to determine whether the fetus has the same disease. Technically, many and various genetic tests can be performed on fetal cells found in the amniotic fluid. For the most part, only relevant tests are performed based on the assessed risk of delivering a newborn with a certain disease. For example, amniotic fluid can be tested to determine whether a fetus is vulnerable to a degenerative muscular disease such as SMA, but this test is only performed when both parents are known carriers of this disease.

Date of the test

The test is mainly performed between week 16 and until the end of week 22 of pregnancy.

In certain cases, the test may also be performed at a later stage of pregnancy (mainly after week 32). In these circumstances, there must be a medical indication for the test and genetic counseling must be provided that recommends it.

Who should be tested

• Age: the test is recommended for all women over the age of 32.
• Abnormal findings in an ultrasound screening: in these cases, the recommendation is to continue investigation of the fetal condition by performing an amniocentesis.
• Results of a biochemistry screening or nuchal translucency screening indicating increased risk of delivering a newborn with down syndrome: in these cases, the recommendation is to continue to investigate the fetal condition by performing the test.
• Abnormal NIPT/ NIPS test: the results must be confirmed by an amniocentesis.
• Increased risk of hereditary genetic disease: for example, when both parents are carriers of one of the diseases being tested for in the genetic screening, or if the parents already have a child with a known genetic disease (the recommendation is given during genetic counseling).

Important to emphasize: even if there is no special medical reason or abnormal findings in the fetus, the amniocentesis may be electively performed.

Recommendations after the test

• You should rest and avoid any exertion for 48 hours (you can receive approval for your place of work).
• You must also avoid sexual relations for 72 hours after the test.

Potential risks and problems

• Miscarriage: according to various studies, the risk of a miscarriage following an amniocentesis is between 1:400-1:1000 (0.1% - 0.25%). If you feel cramping (similar to contractions) in the lower abdomen, a feeling of wetness (possibly indicating your water breaking) or vaginal bleeding, you should seek immediate medical attention from the treating physician or Gynecology ER.
• Infection: an extremely rare complication since the procedure is performed under sterile conditions. If your body temperature rises after the test, if you are experiencing chills or a general feeling of illness, you must seek immediate medical attention from the treating physician or go to the Gynecology ER.
• Insufficient or bloody sample: on rare occasions, the test fails to collect sufficient quantity of cells to extract fetal DNA required to perform the laboratory test, or alternatively - a bloody sample was collected, i.e. the fetal DNA mixed with the mother’s DNA. In these circumstances, you will need to decide whether to undergo another test or rely on the results of the screening tests.
• Inconclusive test results: in other words, results indicate a chromosomal disorder but the impact on fetal health is not sufficiently clear.

Financing the test

There are several medical indications that entitle you to full public funding of the amniocentesis by the Ministry of Health or your HMO. In other cases, the test is funded by the patient or partially funded by the supplementary health services:

• Every woman who is 32 years or older (on the date they became pregnant): the test is funded by the Ministry of Health.
• Every woman under the age of 32 - the HMO will fund the test under the following circumstances:
  
  • Biochemistry screening (from the first or second trimester) indicates increased risk of Down Syndrome and genetic counseling recommended that the test be performed.
  • Results of the fetal nuchal translucency is over 3mm, i.e. - elevated nuchal translucency.
    NIPS/NIPT test - abnormal.
• Woman under the age of 32 who has another medical reason, or who received a medical recommendation following genetic counseling: will be entitled to Ministry of Health funding once it received confirmation from the Genetic Department.

Exercise of the eligibility

• If you are eligible for Ministry of Health funding of the test: you can directly contact one of the approved institutes to schedule an appointment for the amniocentesis.
• If you are eligible for HMO funding for the test: you must find out additional details with the HMO.

Additional amniocentesis tests

There are other tests that can be privately performed on amniotic fluid that was collected during the test, such as:

• Tests that enable a rapid result to detect Down Syndrome (generally within 2-3 days), or a FISH test or a QF–PCR test.
• Growth of amniotic fluid cells collected during the test by the end of the pregnancy, so that if a finding is discovered later in the pregnancy that requires the examination of the fetus, you will not have to undergo another puncture.
• Exome test, a comprehensive genetic test of all functional units in genes, or genome test of the entire fetal genome. Today, these tests are not recommended during a pregnancy in which no significant abnormal findings were detected.

Information about these, and other tests, which are performed on amniotic fluid can be obtained during genetic counseling or at the site where you will undergo the amniocentesis. In any case, it is important to emphasize that these tests are private and not funded by the Ministry of Health or the HMO.