Amniocentesis, chorionic villus sampling and fetal blood sampling
In our offer, you will find conclusive tests such as amniocentesis, chorionic villus sampling and fetal blood sampling. These kinds of examinations are a method of sampling fetal cells, aiming to determine whether a baby is healthy or suffers from a genetic syndrome. Sampling fetal cells by an experienced specialist is almost completely safe and in 99% of cases does not influence the course of the pregnancy.
These examinations are recommended to patients in the following cases:
- increased risk of genetic disorders calculated on the basis of screening tests (ultrasound scan ± biochemical test, NIPT (Neobona, Harmony, NIFTY), age above 40),
Screening tests are not conclusive, they tend to be over-detective to some extent, therefore, in each questionable case, it is recommended to undergo a “stronger” diagnostic examination.
- congenital fetal defects detected in ultrasound,
Detecting a congenital fetal defect is an indication to perform fetal genetic testing. Knowledge obtained from genetic results allows to consult a patient adequately, and above all, to plan the further course of pregnancy and delivery.
- family history indicating the risk of genetic syndromes
- We take chorion and amniotic fluid samples to perform paternity tests. Full discretion is provided in such situations.
Amniocentesis, chorionic villus sampling and fetal blood sampling are carried out by Agnieszka Nocun MD, PhD and Marcin Wiechec MD, PhD. The laboratory section is covered by a team of cytogeneticists from KARIOGEN laboratory in Krakow. In some cases, the samples are sent to Warsaw. Before the procedure, we recommend a genetic consultation, it is possible to set a convenient date of the appointment at the reception desk. Most frequently, the samples are collected on Wednesdays; in some urgent cases it is possible to collect samples on a different day.
The whole procedure is not as complicated as it seems, therefore, after taking the samples most patients admit that “it wasn’t that bad”. We do not require any special preparation. A patient should not fast before the examination. If a patient feels pain, she can take No-spa 30 minutes before collecting the sample. In each case, we begin with a conversation and an analysis of the results, which indicated that there is a need for the procedure. An accompanying person might be present during the conversation. We explain the course of the procedure and possible complications in detail. The samples are usually collected with the use of a fine needle inserted through abdominal walls; transvaginal sampling is extremely rare. We answer all patients’ questions and we assure a free-of-charge check-up examination in the following day or two after the procedure.
Please note that performing an examination safely is our priority and it results from our technique and experience (1.5 years of practice in the Center of Fetal care of Imperial College Healthcare in London; one of seven in Poland Certificate of Fetal Medicine Foundation in scope of invasive testing during pregnancy). This guarantees pregnancy safety in above 99%. All diagnostic tests are carried out at an outpatients’ centre without a need to admit a patient to a hospital.
In our opinion, consultation and qualification for a procedure in every case should be performed by a specialist who carries out such procedures on a daily basis because we frequently encounter views on this subject based on outdated data and an obsolete experience.
Chorionic villus sampling
It is taking a sample of chorion cells (they have the same chromosomes as the fetus) for genetic analysis. It is an examination performed in a local anesthesia, transabdominaly using a thin needle, or transvaginaly with the use of a canula (depending on the localization of a chorion). At our centre, almost 100% of chorionic villus sampling is carried out transabdominaly using 20G needle which is three sizes thinner than the one used in the majority of centres in Poland and abroad. It allows us to minimize the risk of miscarriage. The best time to undergo the procedure is after 11 weeks. Chorionic villus sampling is possible before 11 weeks, however, in accordance with recommendations, we wait until the proper development of baby’s limbs is completed in the first trimester.
A benefit of this examination is that a needle/canula does not enter an amniotic cavity, which is the case during amniocentesis. As in the amniotic cavity a baby is found, many specialists in the world regard this method as a safer one. The risk of miscarriage after a chorionic villus sampling is specified at 0.5% = 1/200 (on the basis of a research of Prof. Podobnik from Zagreb [1,2]).
Chorionic villus sampling has a great time saving advantage, therefore, in majority of cases in the world it effectively replaces amniocentesis. Let us imagine often occurring situation, when in the first trimester of pregnancy, e.g. at 12 weeks an increased nuchal translucency (NT) is detected. Thanks to the sampling availability, we can perform a conclusive examination even on the same day and receive the result in two weeks which would be around 14 weeks. If we proposed amniocentesis in this case, a sample would be extracted at 16 weeks even though we have had suspicions for 4 weeks (additional stress for a patient) and the result would not be ready before 18 weeks. Chorionic villus sampling has not become a tradition in Poland, thus it is difficult to find reliable information on this topic in Polish language. Dr. Wiechec brought this method to Krakow thanks to his work at Imperial College in London, where he has been learning from the best experts on this matter in the world.
In 1% of laboratory failure we carry out amniocentesis free of charge.
It is apparent that a great amount of centres without the option of early karyotype assessment in their offer or having poor experience in chorionic villus sampling will try, even unknowingly, to delay diagnostic process to the stage of amniocentesis.
Since October 2010 we have introduced the fastest method, called direct overnight karyotyping, which allows to obtain an initial result within 24 hours since sampling. It is not a test similar to FISH type or QF-PCR type, which consist in probing only chosen chromosomes. In our method all chromosomes are assessed within 24 hours.
It is a diagnostic examination consisting in inserting a thin needle into an amniotic cavity and extracting a sample. The place of inserting the nedle depends on the position of the fetus, always in a safe distance from the baby. In the amniotic fluid, cells of an amniotic membrane, cells of a fetal digestive tract, mucosa, urinary system, respiratory tract and exfoliated epidermis can be found. On their basis, chromosome assessment in a genetic laboratory is performed. The most important part of the examination is a proper preparation and planning of the procedure individually for every patient. For amniocentesis we use 22G needle which is two sizes thinner than needles used at many centres in Poland. In this way, we minimize the risk of miscarriage. Sample extraction time alone takes 2 minutes. The best time to undergo the procedure is after 15 weeks. The final result is received from the laboratory after 2 or 3 weeks.
In case of anomalies suspicion at the stage of the first trimester (NT scan stage; 11-14 weeks) we propose diagnostic test allowing for an earlier chromosome assessment – chorionic villus sampling because waiting several weeks only for a possibility to perform amniocentesis and another two weeks for a result is unjustified. The majority of centres in Poland are unable to perform chorionic villus sampling and sometimes, even unintentionally, do not inform about such an examination, which extends diagnostic process (suspicion ab. 12 weeks, amniocentesis results not before 18 weeks).
Amniocentesis is usually proposed in case of stating or suspecting an anomaly after 15 weeks of gestation. The risk of miscarriage after amniocentesis is specified at 0.5% (=1/200) on the basis of Canadian research.
Fetal Blood Sampling
It is an examination carried out in a local anesthesia consisting in collecting a blood sample from an umbilical cord and assessment of blood morphology and chromosomes of a baby. The best time to undergo the examination is after 19 weeks. It is used in the fast exclusion of genetic syndromes and peripheral blood flow disorders of a baby, e.g. anemia and thrombocytopenia.
It is a safe examination in 99% of cases. The examination technique is similar to the one used during an amniocentesis and in many cases, is safer because often we do not need to enter amniotic cavity (“baby’s house”) inserting a needle through a placenta directly into an umbilical cord. Considering fetal blood sampling, we always individually assess whether conditions allow us for safe material extraction.
Such an examination is proposed usually at a later stage of pregnancy, e.g. in a situation when a diagnosis of potential genetic disorder was made late. For instance, duodenal atresia characteristics appear in the third trimester and it happens that a patient comes to our centre at 30 weeks pregnant. This disorder may have a connection with the Down syndrome, which would be essential to exclude. Collecting a blood sample from an umbilical cord gives results in between 4 and 7 days.