BIOPSY CHORIONIC VILLUS SAMPLING (CVS) EARLY DETECTION OF SEX, AMNIOCENTESIS, CORDOCENTESIS
What procedures are used to investigate the genetic basis of fruit?
As samples for prenatal diagnosis, in order to investigate the genetic basis of fruit, is now commonly taken chorionic villi, amniotic fluid and fetal blood.
Sampling of chorionic villus sampling (CVS)
In the early diagnosis of hereditary disorders, taking a sample of chorionic villi (chorionic villi sampling - CVS) in recent years become increasingly popular. Basically the idea is that chorionic villus sampling can be used for prenatal diagnosis is the fact that their chromosomal and genetic characteristics are identical to fetal. The main advantage of this method lies in the fact that the disorder is hereditary basis of the fetus revealed very early, during the first trimester of pregnancy, the fast (up to 48 hours of intervention) and the easy way, with virtually the same risk to mother and fetus as well as with other methods. If hereditary disorder is stated, abortion is performed in a simple manner prior to 10 weeks of pregnancy. Because determination of fetal karyotype reveals sex of the fetus, this intervention is advised for the patients who are at risk for transmission of diseases related to sex chromosomes. Transabdominal approach is by far the most popular method for obtaining chorionic villus sampling.
The procedure is performed under local anesthesia and is certainly the most comfortable for the patient. A pregnant woman lying on the bed, and an ultrasound examination prior to intervention in order to assess the viability of pregnancy and gestational age. By determining the position of chorion frondosum starts planning of the shortest path a needle must go through. Then, a special needle (needle-guide with mandrin), pierces the abdominal wall and uterine wall until frondosum chorion (placenta), while not disturbing the area in which the embryo is, and aspires to a certain amount of chorionic villi for cytogenetic analysis. The whole procedure is performed on an outpatient basis, and immediately after the procedure the patient can return to normal activities. Not later than 48 hours after intervention, patients receive the results of cytogenetic analysis of fetal-karyotype.
Amniocentesis - taking a sample of amniotic fluid (AC)
Amniocentesis involves taking amniotic fluid from which then can be analyzed a number of ingredients. In order to investigate the genetic basis of fruit interventions are usually planned during the second trimester of pregnancy. Although contemporary ultrasound devices allow safe sampling of amniotic fluid earlier, the ideal time for intervention is the period between 16 and 18 weeks of pregnancy. During this period, the number of fetal cells in amniotic fluid is sufficient, and the ratio of vital cells and not vital optimal. Given the gestation period during which the intervention is performed in the literature it is called early amniocentesis. The amniotic fluid can be taken after the second trimester of pregnancy.
This intervention is called late amniocentesis and is performed in order to assess the condition of the fetus (in Rh-alloimmunization, for example.), Or to determine the degree of maturation (maturity) of the fetal lungs and planning delivery (forward AC). Ultrasound examination notes the vitality of the fetus, estimated gestational age, amniotic fluid and placental position, and eventually plans to put a needle to an optimal "pockets" of amniotic fluid from which the sample is taken. Syringe aspirate 15-20 ml of amniotic fluid, which heads to the desired view (cytogenetic analysis).
Fetal blood sampling - cordocentesis (CC)
Cordocentesis (cordocentesis - CC) includes transabdominal fetal puncture of the umbilical cord and taking fetal blood sampling. Because of its invasiveness and the slightly higher risks of this intervention is only in strictly indicated cases, gestational age of pregnancy would have to exceed 20 weeks. The result is obtained within seven days.
Prenatal invasive diagnostic procedures are very safe. Complications in the form of scarce bleeding and uterine contractions after the procedure are rare, usually benign and short-lived. Infection and rupture of fetal membranes are very rare. The possibility of miscarriage is between 0.5 and 2% depending on the applied methods, and operator experience. Diagnostic safety of prenatal invasive procedures was higher than 95%.
In certain cases it is not possible to determine the exact karyotype of the fetus, and these are usually:
- Insufficient amount of material, ie, the inability to obtain sufficient numbers of cells in the division for proper analysis. In such cases, repeating of intervention is proposed or some other diagnostic procedures are advised.
- Twin pregnancies carry a risk that can not be confidently localize the placenta belonging to each of the embryos.
- Placental mosaicism - obtained a sample of 1% of patients include a mixture of normal and abnormal cells. In this case, cytogenetic findings may not correspond with the karyotype of the fetus.
There is no 100% safe prenatal diagnostic methods. Approximately 2-3% of all pregnancies are associated with genetic damage to the fetus that can not be detected by determining the hereditary basis (karyotype) of the fruit.