What is amniocentesis?
During amniocentesis, the doctor removes some amniotic fluid from the amniotic sac via a hollow needle. Fetal cells float in this amniotic fluid and can be isolated in the laboratory and multiplied in a cell culture. After about two weeks, sufficient genetic material is then available to be examined for errors and deviations.
In addition, the concentrations of two proteins in the amniotic fluid are determined: alpha-fetoprotein (alpha-1-fetoprotein, α1-fetoprotein, AFP) and the enzyme acetycholinesterase (AChE). Elevated levels of these proteins may indicate malformations of the spine or abdominal wall, especially if both levels are elevated at the same time.
The protein AChE is an enzyme of the nervous system and is also elevated in a neural tube defect.
Amniocentesis: an overview of detectable diseases
The genetic material of the child obtained by amniocentesis is analyzed in detail in the laboratory. On the one hand, the structure and number of chromosomes can be examined – the genetic material DNA is organized in the form of 23 double chromosomes. On the other hand, the DNA itself can also be analyzed.
Possible genetic abnormalities that may arise during chromosome analysis are:
- Trisomy 21 (Down syndrome)
- Trisomy 18 (Edwards syndrome)
- Trisomy 13 (Pätau syndrome)
In addition, chromosome testing can determine the sex of the child – some genetic diseases only occur in one of the two sexes.
DNA analysis can reveal familial hereditary diseases and inherited metabolic disorders.
In addition to genetic material, the amniotic fluid sample itself can also be analyzed. This biochemical analysis can detect the following diseases:
- Clefts in the spinal column (open back = spina bifida)
- abdominal wall defects (omphalocele, gastroschisis)
The biochemical examination can also detect any blood group incompatibility between mother and child (from the 30th week of gestation).
If a premature birth is imminent, doctors can also use the amniocentesis to find out how far the child’s lungs have already matured. If they are still underdeveloped, medication can be used to promote lung maturation.
When is amniocentesis recommended?
Amniocentesis is recommended to many pregnant women when there is an increased risk of defects in the child’s genetic material for certain reasons. Such reasons may include:
- Age of the pregnant woman over 35 years
- abnormalities in ultrasound or first trimester screening
- familial hereditary diseases such as metabolic or muscular diseases
- an older sibling with a chromosomal disorder
- previous pregnancies with a neural tube defect or miscarriage due to a chromosomal disorder
If one of the above reasons exists, the health insurance company will cover the costs incurred for the amniocentesis.
Amniocentesis: When is the best time?
Depending on the issue and the problem, amniocentesis is sometimes performed at a later time (i.e. after the 19th week of gestation).
What exactly is the amniocentesis procedure?
The Genetic Diagnostics Act stipulates that every pregnant woman must be informed in detail about the procedure, benefits and risks of the voluntary procedure before amniocentesis and must give written consent to the examination.
An amniocentesis is performed on an outpatient basis in a specialized practice or clinic. Before the puncture, your gynecologist will use ultrasound to check the position of the baby and mark the puncture site on your abdomen. After careful disinfection, he or she punctures the amniotic sac with a thin hollow needle through the abdominal wall and the uterine wall and draws up between 15 and 20 milliliters of amniotic fluid. In the laboratory, the cells contained in the extracted fluid are further processed.
Amniocentesis takes between five and 15 minutes. Most women do not find the procedure painful. Local anesthesia is usually not necessary.
After the amniocentesis
If pain, bleeding, amniotic fluid leakage or contractions occur after the amniocentesis, you must see a doctor immediately!
When will the results of the amniocentesis be available?
It takes between two and three weeks until the amniocentesis results are available – a time that is often very stressful for the parents-to-be and their relatives.
Amniocentesis: risk and safety
Complications are rare with amniocentesis. However, like any procedure, amniocentesis carries risks:
- miscarriage (risk with amniocentesis 0.5 percent; for comparison: with chorionic villus sampling 1 percent)
- premature rupture of the membranes
- contractions of the uterus
- bleeding (rare)
- infections (rare)
- Injuries to the child (very rare)
The result of amniocentesis provides a definite result 99 percent of the time for chromosomal defects and 90 percent of the time for neural tube defects. Sometimes a parental blood test, ultrasound, further amniocentesis, or fetal blood test is still needed for confirmation.
Amniocentesis: Yes or no?
The results of an amniocentesis do not tell us anything about clefts in the face, heart defects or malformations of the hands and feet. A high-resolution ultrasound examination between the 20th and 22nd week of pregnancy can sometimes provide information about these.
In principle, the benefits and risks of the procedure must be carefully weighed on an individual basis.
Amniocentesis: A positive result – what now?
If you decide to have a prenatal examination, you should consider in advance what consequences a positive result would have for you. Chromosomal damage or hereditary diseases cannot be cured. The physical impairments in the child can vary greatly depending on the damage and cannot always be clearly predicted.
