Biology XII Content
Amniocentesis is the medical procedure used in prenatal diagnosis of chromosomal abnormalities and fetal infections, in which a small amount of amniotic fluid from amniotic sac of pregnant woman is sampled, which contains fetal tissues, and the fetal DNA is examined for genetic abnormalities.
It was developed by Richard Dedrick, and can be used for prenatal sex discernment and hence this procedure has legal restrictions in some countries.
A local anesthetic is given to the mother in order to relieve the pain felt during the insertion of the needle used to withdraw the fluid. Then a sterilized hypodermal needle is usually inserted through the mother’s abdominal wall, then through the wall of the uterus, and finally into the amniotic sac to take out amniotic fluid.
If used for prenatal genetic diagnosis, fetal cells are separated from the extracted sample. The cells are grown in a culture medium, then fixed and stained. Under a microscope the chromosomes are examined for abnormalities like Down’s syndrome, Sickel cell anemia etc. It is also used in detecting sex of baby.
1) Genetic diagnosis:
- Down syndrome
- Fragile X
- Rare, inherited metabolic disorders
- Neural tube defects
2) Determination of sex of foetus.
- Amniocentesis is performed between the 15th and 20th week of pregnancy; performing this test earlier may result in fetal injury
- Complications of amniocentesis include preterm labor and delivery
- Chance of infections and miscarriage
- Ethical problems arise when parents decide for an abortion following the test results when there is a baby girl in the womb of mother
- It is expensive process