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PRENATAL DIAGNOSIS AND FETAL THERAPY
Invasive techniques for prenatal diagnosis
If necessary and after a doctor’s recommendation, a full range of invasive methods for prenatal diagnosis is performed at Nadezhda Hospital – amniocentesis, chorionic villus sampling (CVS), cordocentesis.
Invasive diagnostic procedures are recommended in cases when there are serious suspicions about a problem with the foetus, which must be proven by the application of the appropriate invasive diagnostic method.
Amniocentesis
At what stage of pregnancy is amniocentesis performed?Usually between the 15-th and the 19-th week.
If a structural defect is detected during fetal anomaly scan amniocentesis may be performed at a later stage.
Age over 36, high risk of screening for Down’s, structural abnormalities, structural features (also called markers), inherited diseases in the family, previous child with chromosomal abnormality, changes in the karyotype of the parents, etc. In each individual case, an examination is carried out to establish the indications for the procedure and, if necessary, a genetic consultation to determine the specific type of genetic analysis to be applied.
Complete blood count (CBC), differential blood count, Fibrinogen INR, blood group rhesus factor, Hepatitis B, AIDS, Wasserman.
After cleaning the abdominal wall with disinfectant solution, the amniotic bladder is punctured through the patient’s abdomen using a fine needle and a small amount of amniotic fluid is withdrawn. This fluid contains cells from the baby that can be subjected to various types of genetic analysis.
The procedure is mildly painful, and the sensation is described as similar to a muscle injection or pain during menstruation. The manipulation lasts a few minutes and is performed under constant ultrasound monitoring, the aim of which is to determine the position of the foetus and placenta, so that the optimal site for puncture can be selected.
Important! In rhesus-negative patients, anti-D immunoglobulin must be administered after chorionic villus sampling (CVS), amniocentesis and cordocentesis.
Since the procedure is performed under constant ultrasound control, the risks of injury to the foetus and the mother’s organs are minimal. According to studies, the risk of miscarriage after amniocentesis is estimated at 1:100-1:200 pregnancies. It should be borne in mind that a certain proportion of late miscarriages occur between 15-19 weeks, (i.e. in the period when amniocentesis is performed) and without any invasive manipulation. The risk of pregnancy loss after amniocentesis is maximal in the first week after the procedure.
It is recommended to rest for several days after amniocentesis, refrain from sports and from lifting heavy objects.
Rapid DNA analysis and FISH – 4 days, cytogenetics – 3 weeks, chip – 7 days.
Cordocentesis
Cases in which a cordocentesis has to be performed are a late malformation or a suspected chromosome number abnormality in the foetus at late gestational term.
The advantage of the procedure is that due to the larger amount of cells in the blood, the chromosome number can be directly examined without the need for culture.
This way, the result is clear after 4 to 7 days. In comparison, amniocentesis results take three weeks.
Important! In rhesus-negative patients, anti-D immunoglobulin must be administered after chorionic biopsy, amniocentesis and cordocentesis.
Cordocentesis may be performed after completion of the 20-th gestational week.
In rare cases and by way of exception, cordocentesis may be performed during the 19-th gestational week.
At an earlier stage of pregnancy, due to the small size of the umbilical cord and the greater risk to the pregnancy, this procedure is not recommended.
The risk to pregnancy with cordocentesis is comparable to that of amniocentesis.
Chorionic villus sampling (CVS)
Between 11-th and 13-th gestational week. At this early time, chorionic biopsy is the only invasive investigation possible.
Age over 36, high risk of screening for Down syndrome or other chromosomal abnormalities, structural abnormalities, structural features (also called markers), inherited diseases in the family, previous child with chromosomal abnormality, changes in the karyotype of the parents, etc. In each individual case, an examination is carried out to establish the indications for the procedure and, if necessary, a genetic consultation to determine the specific type of genetic analysis to be applied.
Complete blood count (CBC), differential blood count, Fibrinogen INR, blood group, rhesus factor, Hepatitis B, AIDS, Wasserman.
CVS is an outpatient procedure, unless the patient wishes the examination to be performed under clinical pathway. In this case, a hospital stay of two nights is required.
After cleaning the abdominal wall with a disinfectant solution, the placenta is punctured through the patient’s abdomen using a thin needle under ultrasound control and several so-called “chorionic villi”, which are small pieces of the placenta, are pulled out using vacuum. The cells of the placenta contain the same genetic material as that of the foetus and can be subjected to various types of genetic analysis.
The procedure is mildly painful, and the sensation is described as similar to a muscle injection or pain during menstruation. The procedure lasts about a minute and is performed under constant ultrasound monitoring, the purpose of which is to determine the position of the foetus and placenta, so the optimal site for puncture can be selected.
Since the procedure is performed under constant ultrasound control, the risks of injury to the foetus and the mother’s organs are minimal. According to studies, the risk of miscarriage after chorionic biopsy is estimated at 1:100-1:200 pregnancies. It should be borne in mind that a certain proportion of late miscarriages occur between the 15-th and 19-th gestational week without invasive manipulation. The risk of pregnancy loss after chorionic biopsy is maximal in the first week after the procedure.
At Nadezhda Hospital, chorionic biopsy is performed under clinical pathway N. 143 for insured patients.
See also
Non-invasive prenatal diagnosis (NIPD)
Fetal surgery
First trimester combined screening
Fetal anomaly scan
