Amniocentesis: meaning, time frame and procedure

Amniocentesis is a test that can be performed during pregnancy. It is referred to as an invasive prenatal diagnostic procedure, which means that the examination involves intervention in the body of the expectant mother. Amniocentesis is used to detect certain infectious diseases, genetic disorders and abnormalities in the unborn child’s genetic material. The procedure is rarely performed and will only be offered if there is reasonable suspicion of a serious disorder.

Reasons for performing amniocentesis

Amniocentesis is not a common examination during pregnancy. Experts will only recommend it in the following cases:

• If the results of an ultrasound examination or the first-trimester test are at all unusual.
• In cases where there is an increased risk of genetic disorders.
• If a doctor suspects the unborn child may have an infection.

Amniocentesis is more common in late pregnancies, as the risk of trisomy increases with the age of the expectant mother. However, even in women who have children later in life, the examination is only performed in cases of reasonable suspicion.

At what point can amniocentesis be performed? Amniocentesis is usually performed from the 15th week of pregnancy onwards. Before the 15th week of pregnancy, the risk of miscarriage due to the procedure is higher, and the results are not yet reliable. Doctors usually carry out the examination between the 15th and 18th week of pregnancy.

How does amniocentesis work? First, your doctor will explain the procedure and inform you of the potential risks. You will have the opportunity to clarify any questions you may have before you give your written consent to the procedure. The doctor will use an ultrasound to check the baby’s position. They will then insert a hollow needle through your abdominal wall into the amniotic sac, before extracting around 15 to 20 millilitres of amniotic fluid. The procedure itself takes around 15 minutes and is not usually painful, so most women choose not to have a local anaesthetic. After the examination, you will be kept in the practice or hospital for another 30 minutes or so for observation.

What happens after amniocentesis? The puncture site closes immediately after the sample has been taken. You may experience pressing pain in your lower abdomen for a short time. Avoid physical exertion and sexual intercourse for two days after having amniocentesis. You will receive your results after 10 to 14 days. During this time, the laboratory will culture your baby’s cells and examine them for chromosome structure and number.

Amniocentesis provides reliable findings – its results are 99% accurate for chromosomal abnormalities and 90% accurate for neural tube defects. There is also a rapid amniocentesis test. Experts also refer to this as “fluorescence in situ hybridisation” (or a FISH test). This type of amniocentesis produces results in just 24 hours. The disadvantage is that it is somewhat less reliable, as it does not give the laboratory enough time for a long-term culture of the baby’s cells.

By the way, amniocentesis is also possible if you are pregnant with twins. Depending on the situation, your doctor may decide to perform a single or double needle insertion.

Amniocentesis reveals chromosomal disorders (or chromosomal abnormalities) as well as infections and other illnesses. These include:

• Trisomy 21 (Down’s syndrome): amniocentesis identifies trisomy 21 on the basis of chromosome 21. There are usually two copies of this chromosome, but with trisomy 21, there are three. Trisomy 21 affects mental and physical development. The severity varies from person to person.
• Trisomy 18 (Edwards’ syndrome): trisomy 18 describes the presence of a third copy of chromosome 18. This results in organ malformations. Those affected have only a slim chance of survival.
• Trisomy 13 (Patau’s syndrome): People with Patau’s syndrome have three copies of chromosome 13 instead of two. Here, too, the chances of survival are low. It can also lead to malformations.
• Neural tube defects: amniocentesis also detects neural tube defects such as spina bifida, a cleft formation in the spine that sometimes causes paralysis and incontinence.
• Infectious diseases: infectious diseases can also be detected using amniocentesis. Examples include toxoplasmosis, a common infectious disease caused by contaminated food. Amniocentesis can help to determine whether the unborn child has become infected.
• Metabolic disorders such as phenylketonuria (which prevents the normal metabolism of certain amino acids) and neutral lipid storage disease.
• Muscle disorders such as Duchenne muscular dystrophy, which leads to progressive muscle atrophy and reduced life expectancy.

Please note that this is not an exhaustive list.

Amniocentesis: positive results

A positive result from amniocentesis often raises many questions for expectant parents. In this situation, comprehensive medical advice is particularly important. Your doctor will explain what the diagnosis means and what treatment options are available. Take the time to consider your options and talk to your doctor about which course of action is best for you. Support from family and friends is also very important at this time.

Amniocentesis is considered a safe procedure, but it does carry a certain risk of complications:

• The risk of miscarriage is up to 1%. This applies for about three to five days after the examination.
• In rare cases, amniocentesis can lead to premature rupture of the amniotic membranes.
• Women may also experience bleeding or uterine contractions, although this is uncommon.
• Injury to the unborn child as a result of amniocentesis is very rare.

The wait for the results can be stressful for many parents. They may experience a great deal of uncertainty and worry during this time. Then there are the moral questions to consider: how do I deal with the diagnosis? What decisions do I have to make? Every family experiences this situation differently. An open discussion with specialists can help you deal with the situation.

Aside from amniocentesis, there are other invasive and non-invasive prenatal diagnostic methods. Common procedures include the following:

• Blood tests: blood tests are non-invasive, low-risk and therefore usually the first choice. They can provide evidence of genetic disorders and chromosomal abnormalities. In some cases, it may be advisable to perform amniocentesis in addition to a blood test, since only amniocentesis and other invasive methods can provide reliable results.
• Chorionic villus sampling: in chorionic villus sampling, a specialist takes a small tissue sample from the placenta. This sample is then used to provide information about the baby’s chromosomes. Chorionic villus sampling is performed from the 11th week of pregnancy onwards and may be done up to the 14th week of pregnancy. You should talk to your doctor about whether amniocentesis or chorionic villus sampling would be advisable for you.
• Cordocentesis: in this procedure, specialists obtain blood from the unborn child by puncturing the umbilical cord vessels. The results of this examination are also highly reliable. Cordocentesis can be carried out from the 18th week of pregnancy.

You decide which prenatal tests you want to have. It’s best to talk to your doctor about the benefits and risks. Making informed decisions provides peace of mind and strengthens trust. The important thing is that you take enough time to consider your options. Your health and that of your child are the most important aspects.