By testing 3 substances in the mothers blood, in the 16th week of pregnancy (Alpha-Feto-Protein-AFP, HCG, Estriol=AFP-plus) signs of a mongoloid child can be picked up. From these results, special mathematical programmes can calculate any higher risk. This must not necessarily be proof, but depending on the results, a genetic consultation, an ultrasound or amniocentesis will be necessary after consultation with the doctor. Pathological results in any of these 3 substances (AFP-plus) are a good guide for disorders in the spine, head, kidneys or abdominal wall.
2. PAPP-A-Test (11th to 14th week of pregnancy):
A combination of the serum level of PAPP-A (Pregnancy Associated Plasma Protein) and the free beta HCG in the mother’s blood. In contrast to the Triple Test, this can be performed earlier (11th to 14th week of pregnancy) and supply particular information over Trisomie 21. The detection rate lies by approximately 70%, and a false positive result appears in about 5% of all tests. When this test is conspicuous, more invasive examinations (see below) are advisable.
3. Foetal Cells in the Mothers Blood.
In every pregnancy, foetal cells (lymphocytes, trophoblast cells, erythrocytes) circulate in the mother’s blood. These cells can be analysed for chromosomes 13, 18 and 21 with the help of special probes. The gender can also be determined. These techniques are still not clinically tested and must be looked upon as experiments.
B: INVASIVE METHODS OF CHROMOSOME ANALYSIS
1.) Chorion villi biopsy
This method is performed by taking tissue from the placenta in the 10th –11th
Week of pregnancy. The results are available about one week later. If these results are unclear, (only placenta cells, and not those of the child are tested) an amniotic fluid punction must be carried out for clarification. The risk of miscarriage after amniotic fluid punction is about 1%.
2 ) Amniotic Fluid Punction-Amniocentesis
A sample of the child’s cells are taken by puncturing the abdominal wall under ultrasound control. These cells are then bred for a short time in a special genetic laboratory and then analysed. The final results are very reliable, but the whole procedure takes about 3 weeks .The risk of miscarriage after amniocentesis is also about 1%.
3.) Placenta Biopsy
If there are any significant abnormalities in the ultrasound examinations, kartotyping is recommended. The results are available in one day. In the future earlier results will be available with the help of FISH and PCR techniques.
>4. Cordocentese
Available only in special centres with equipment for emergency caesareans. This procedure can supply fast results concerning cytological diagnosis, foetal blood analysis, and judge the condition of badly retarded foetuses . It also makes inter uterine therapy possible. eg. erythrocyte and thrombocyte transfusion.
C) Ultrasound Diagnosis
For over 40yrs, ultrasound examination has provided one of the safest and most accurate methods of diagnosis. Up to now, no harmful effects to mother or child have ever been reported.
Ultrasound is used in obstetrics for:
Diagnosis and confirmation of pregnancy.
Assessment of the normal development of the child.
Diagnosis of multiple pregnancy.
Assessment of the placenta and amniotic fluid.
D) Examination of the Embryos before they are Transferred to the Uterus = Pre Implantations Diagnosis (PID)
When the embryo is 3 days old, (8 or more cells) single cells are extracted and examined for chromosome defects-genetic disorders. If the cells show any defects the embryo will not be transferred, therefore there will be no pregnancy.
At the moment PID is illegal in Austria, Germany and switzerland. It is legal in Italy (also see : rgi@flash.net ).