What is the purpose of invasive prenatal diagnostics?
Prenatal diagnostics enables the recognition of certain foetal disorders prior to delivery. One possible benefit of prenatal diagnostics is a chromosome count determination in the foetus. Among the most frequent and commonly known disorders with a different numbers of chromosomes is Down syndrome.
Do all pregnant women undergo this examination?
No, this examination is done only for women with an elevated risk of chromosomal aberration.
The risk factors include:
– maternal age greater that 35 years at the time of delivery
– positive biochemical screening – the risk is greater than one affected child in 270.
– finding of ultrasound markers – a sign of chromosomal aberration in sonographic examination. One of the most reliable is the accumulation of subcutaneous fluid on the neck of the foetus in the 11th-13th week of pregnancy.
– incidence of chromosomal aberration in the family
Sampling of amniotic fluid — amniocentesis
I want to be 100% certain that our child does not have Down syndrome.
This test is able to distinguish irregularities in the number and shape of chromosomes. It is normally done in the 15th-18th week of pregnancy.
What is the principle of this test?
The amniotic fluid contains cells which have been shed from the foetus and its sac. Following the necessary cultivation, the cells are evaluated for chromosome count and structure.
How is this test performed?
In this test, a thin needle is introduced under sonographic control into the amnial cavity through the abdominal wall and about 10% of the total amniotic fluid volume is withdrawn. The intervention is best compared to taking a blood sample from a vein or an intramuscular injection.
How long does it take to get the result?
The result of a chromosome analysis is normally available in 12-14 days. Immediately after the evaluation, the result is posted for your information on our web site www.prenatal.cz under a specific password. Two hard copies are sent to the attending physician.
When PCR is used (see amnioPCR), the results are reported on the day of sampling and posted for your information on our web site www.prenatal.cz under a specific password.
What are the sampling risks?
The greatest risk associated with this test is the possibility of inducing a spontaneous abortion. This risk is quoted to be in the range of 0.5-1.0%. In our clinic, the range is 0.25-0.35%.
What are the advantages of this test?
This is the most frequently performed prenatal foetal examination. The method is relatively safe and accurate, with a minimum of complications or necessary repetitions of sampling.
When is this test inappropriate? The sampling of amniotic fluid poses a higher risk to women with bleeding, uterus toning, cervical incompetence or a general illness, i.e. in those cases where the risk of complications induced by sampling is greater than the risk of foetal problems