This is useful for the detection of a genetic disorder and congenital syndrome before the birth of the child. And helpful for a parent to prepare mentally and medically for the baby coming with disability.
Techniques used in prenatal detection
There are several techniques that can be used for the detection of heredity disorder and congenital syndrome. Some of these techniques are as follow
Amniocentesis is used for prenatal detection of a genetic disorder, by the use of amniotic fluid which should be taken from amnion. Involve aspiration of 15-20 ml of amniotic fluid under the guidance of ultrasonography usually performed after 15-16 weeks of gestation. After this extraction of DNA takes place from sample then PCR is used for amplification of sample DNA. After this analysis of data for detection takes place, if a fetus has any abnormality should be taken under proper medication or should be the termination of pregnancy.
Chorionic Villus Sampling
This technique is 1st developed in China. This used in the first trimester usually in 11-12 weeks of gestation, usually 11 to 12 weeks of gestation. Takes place by transcervical or, more usually, transabdominal aspiration of chorionic villus (CV) tissue under the guidance of ultrasonography. This tissue is fatal in origin and derived from the outer layer of blastocyst. This process is termed as a Placental biopsy when takes place in the later stage of pregnancy. Chromosomes analysis is taking place either by either directly, looking at metaphase spreads from actively dividing cells, or after culture, direct analysis allows provisional results within 24 hours. Fluorescent in-situ hybridization (FISH) probing or DNA analysis by the multiplex ligation-dependent probe amplification technique is used to test for common chromosome aneuploidies (Peter Turnpenny et al).
It is used in placental localization, diagnosis of multiple pregnancies, and also prenatal detection of structural abnormalities which is not associated with the known chromosomal, biochemical, or molecular defect. It is not invasive conveys no known risk to the fetus or mother
It involves visualization of the fetus by means of an endoscope, it is also been used to obtain a sample of tissue from that can be analyzed for prenatal detection. Unfortunately, it is associated with 3%-5% risk miscarriage, this is high risk.
Fetoscopy can also be used for obtaining a small sample from umbilical cord vessels called cordocentesis. An obtained sample is used for chromosomal analysis.
It is used to visualize the fetal skeleton by radiography from 10 weak onward. It has been used in the past to diagnose inherited skeleton disorder. But radiography is dangerous for developing fetus so nowadays it is used only occasionally.
The widespread prenatal screening began with the finding of an association between raised maternal serum α-fetoprotein (AFP) and neural tube defects (NTDs). It can be done by the following method –
Maternal Serum Screening
The sample obtained from 16-week pregnant women, about 75% of cases of open NTDs and 60-70% of all cases of Down syndrome can be detected
Neural tube defect detection by maternal serum screening
It can be performed on 16 weeks’ pregnant mother by assay AFP in mother serum. If the fetus has NDTs level of AFP increase in both maternal serum and amniotic fluid
Down syndrome and other Chromosome Abnormalities (The Triple Test) detection by maternal serum screening
This is detected by screening of maternal serum. In the case of Down-syndrome pregnancy, AFP and unconjugated estriol levels become low in maternal serum, while human chorionic gonadotropin (hCG) level becomes higher than a normal pregnancy.
References and Sources
- 2% – https://www.researchgate.net/publication/10673314_Prenatal_screening_for_open_neural_tube_defects
- 2% – https://www.gfmer.ch/SRH-Course-2016/community-genetics/pdf/Prenatal-genetic-screening-diagnosis-Hamamy-2016.pdf
- 2% – https://quizlet.com/19120087/antepartum-flash-cards/
- 1% – https://youaremom.com/pregnancy/im-going-to-be-a-mom/prenatal-care/prenatal-genetic-testing/
- 1% – https://www.ncbi.nlm.nih.gov/pubmed/1704627
- 1% – https://www.ncbi.nlm.nih.gov/pmc/articles/PMC86213/
- 1% – https://www.aafp.org/afp/2002/0301/p915.html
- 1% – https://wikimili.com/en/Amniocentesis
- 1% – https://radiologykey.com/fetal-mr-imaging-protocols-and-anatomy/
- 1% – https://en.wikipedia.org/wiki/Blastocyst
- 1% – https://clinicalgate.com/prenatal-testing-and-reproductive-genetics/