Invasive prenatal diagnostic testing | amniocentesis, chorionic villus sampling or fetal blood test – what is behind the invasive methods of prenata l diagnostic testing?

Pregnancy is an exciting time for prospective parents, a time which, in most cases, is marked by a mix of pleasant anticipation and suspense but also anxiety. The latter emotion is especially associated with the health component of the prenatal examination methods because the baby’s wellbeing takes highest priority for the mother and father. In this context, invasive prenatal diagnostic testing becomes a matter of interest. Invasive diagnostic tests may detect prenatal anomalies at an early point in time. In the following, we will give you an overview of the available invasive methods of prenatal diagnostic testing and explain the procedures of amniocentesis, chorionic villus sampling and fetal blood tests.

What is invasive prenatal diagnostic testing?

Invasive prenatal diagnostic testing refers to an examination in which a puncture is made through the mother’s abdominal wall. Using a fine needle, a sample of fluid is taken, e.g. amniotic fluid, placental tissue or blood of the unborn child. In most cases, the puncture sample is used for a genetic examination of cell material from the baby but also to test for a gestational infection or, for example, blood type incompatibilities. It cannot be ruled out that invasive methods of prenatal diagnostic testing may involve a risk of miscarriage. Therefore, invasive prenatal diagnostic tests tend to be performed in cases where the likelihood of a disease in the unborn child is higher than the risk of miscarriage caused by the puncture.

What invasive methods of prenatal diagnostic testing can be performed?

Invasive diagnostic tests include:

• amniocentesis
• chorionic villus sampling
• or the fetal blood test performed as part of cordocentesis

Amniocentesis

With this procedure, which may be performed from the 16th or 17th week of pregnancy onward, amniotic fluid is evaluated for the purpose of a chromosomal analysis. About 8 to 10 ml are taken and there is no need for local anesthesia. The procedure, which is performed within about one minute, is guided by concurrent ultrasound monitoring. In order to perform the chromosomal analysis, cells taken from the amniotic fluid must be multiplied. A result is available in about 10 to 14 days. At the same time, a rapid test may be performed to detect a possible chromosomal disorder. Moreover, amniocentesis may detect proteins in amniotic fluid that may indicate the presence of a gap in the area of the abdominal wall or the vertebral column. If you wish to undergo a test for potential metabolic disorders, these may also be detected by amniocentesis. The findings obtained from all of these tests are highly informative. If, in rare cases, findings should be inconclusive, further examinations may yield results. The risk of miscarriage resulting from the prenatal examinations is estimated to be as low as 0.25 to 1%. It is also essential that the mother-to-be allows herself to indulge in rest and relaxation.

Chorionic villus sampling or fetal blood test (cordocentesis)

From the 12th to 13th week of pregnancy onward, you can undergo chorionic villus sampling. This is a procedure during which placental tissue is taken. The procedure usually lasts no longer than a minute, and after only 1 or 2 days, initial results may become available in the form of a short-term culture. If a long-term culture is developed, results will be available after 8 to 10 days.

A fetal blood test is taken as part of a cordocentesis, which is an invasive prenatal diagnostic procedure involving a puncture of the umbilical cord. About 1 or 2 ml of fetal blood are taken. Cordocentesis may be performed, approximately, from the 18th week of pregnancy onward, and this form of invasive diagnostic testing also is not entirely free of risks. After only 2 or 3 days, you can expect to receive a result of the chromosomal analysis. Cordocentesis may help to diagnose fetal infections and blood disorders. The risk of miscarriage is similar to that of amniocentesis. Here, too, a follow-up examination should be performed by your gynecologist after 1 or 2 days and you should avoid physical exertion.

Get informed about invasive methods of prenatal diagnostic testing now. Feel free to find out more about amniocentesis, chorionic villus sampling or the fetal blood test at Pränatalzentrum Stuttgart.

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