PGD(Prenatal Genetic Diagnosis)
Prenatal genetic diagnosis is done by cytogenetic, molecular genetic, and molecular cytogenetic methods & advanced ultrasonography. An increasing number of monogenic diseases can be diagnosed prenatally by either genetic or biochemical testing, but Polygenic and multifactorial diseases cannot be reliably diagnosed by genetic testing at present, although a number of malformations can be ascertained prenatally by ultrasonography.
The prenatal diagnosis of chromosomal abnormalities by karyotyping: INDICATIONS ARE-
Maternal age:Chromosomal anomalies increases with maternal age.Ex:Trisomy 21 (Down syndrome).
Following an abnormal result shown in non-invasive screening.
Following an ultrasound finding which raises the possibility of a chromosomal problem.
In the presence of a known translocation,inversion or insertion in one parent.
A chromosomal anomaly in an existing child. Ex: after the birth of a child with trisomy.
Genetically determined diseases can be divided into three groups:
Genetic carrier screening:
This is a simple blood test to analyse your DNA to know whether it carries a gene for a particular disease and transfer of it to your child.
First trimester screening:
To all woman at 11 or 12 weeks of pregnancy done by ultrasound and blood test. With these we can know some genetic conditions, including Down syndrome.
Cell-free DNA screening:
Also known as noninvasive prenatal screening. This blood test uses the fetal DNA circulating in the mother’s blood to screen for chromosomal abnormalities. It’s the most accurate screening test for detecting the risk of Down syndrome.
Amniocentesis is typically carried out under ultrasonographic control, between 15 and 17 weeks of pregnancy. Around 15 mL of amniotic fluid would normally be aspirated. Chromosomal analysis requires prior to cell culture, after this metaphase chromosomes are analyzed numerically and structurally. Uncultured amniotic fluid can be used to determine levels of alpha fetoprotein (AFP), which is present in increased concentrations in open neural tube defects and other disorders such as abdominal wall defects (e.g., gastroschisis).
Chorionic villus sampling (CVS) and amniocentesis:
These two invasive tests involve inserting a needle into your uterus to collect a sample of complete fetal cells to test for chromosomal abnormalities. These tests can tell you definitively if your baby has a particular condition, but they also have a small risk of miscarriage.