Prenatal diagnostic techniques

Amniocentesis

🧫It is a medical procedure used for prenatal genetic testing for chromosomal  abnormalities, fetal infections as well as for sex determination by analysing the cells of amniotic fluid.

🧫Amniotic fluid is the fluid that fills the amniotic sac and  surrounds the developing fetus.

 🧫It contains fetal cells like multipotent mesenchymal, hematopoietic, neural, epithelial, and endothelial stem cells.

🧬These cells can be used for genetic testing.

🧫To obtain a sample of amniotic fluid from a pregnant woman a long sterile needle is inserted through the abdominal wall into the amniotic sac.

 Uses

📍This process is performed to look for certain types of birth defects. 

📍This prenatal test is generally offered to women who have a significant risk for genetic diseases, 

📍Amniocentesis can be used to  detect the following conditions 

 Down syndrome

 Sickle cell disease

 Cystic fibrosis

 Muscular dystrophy

 Tay-Sachs disease

 Chorionic Villus Sampling

💉Chorionic villus sampling (CVS) is a prenatal test that involves taking a sample of tissue from the chorionic villi of placenta to test for chromosomal abnormalities and certain other genetic problems

 💉This technique can be done as early as the 8th week of pregnancy

💉The chorion is a membranous layer surrounding the foetus.

 💉It consists entirely of foetal tissue. Hence the cells obtained from chorion will have the genetic make up of the foetus.

💉The technique involves insertion of a catheter through the vagina and extracting a small piece of chorionic villus tissue .

 💉Once the tissue sample is obtained, the analysis is done for chromosomal abnormalities.

💉One advantage of chorion villus sampling is that the prenatal diagnosis can be done much earlier than what is possible in amniocentesis.

💉It is also not necessary to culture cells to obtain sufficient amount for biochemical tests.

💉Diagnostic tests can be conducted directly on the tissue samples collected.

Uitrasound scanning: 

🩺Ultrasound imaging systems uses piezoelectric transducers as source and detector. 

🩺Piezoelectric crystals vibrate in response to an alternating voltage, and when placed against a patient’s skin and driven at high frequencies produce ultrasound pulses that travel  through the body.

🩺As they travel outwards and encounter different layers within the body the ultrasound waves are reflected back towards the source.

🩺The returning signal drives the 

crystals in reverse and produces an electronic signal that is processed to construct the  image.

🩺Compared to MRI, ultrasound has the advantages of low cost and portability.

🩺 It is also preferred over X-ray imaging for procedures in which ionising radiation poses a 

 significant risk, such as checking foetal development during pre-natal care

🩺 In order to carry out an ultrasound scan a gel is used to 

minimise reflections from the patient’s skin.

🩺The ultrasound waves used to construct an image are produced and detected using a probe connected to the ultrasound 

machine.

🩺Ultrasound scanning is a useful way of examining many of the body's internal organs, including heart and blood vessels, liver, gallbladder,spleen,pancreas,kidneys.bladder uterus, ovaries,eyes thyroid,parathyroid glands,scrotum (testicles) etc.

🩺It is also used to monitor growth and development of foetus during pregnancy.