Amniocentesis and Chorionic Villus Sampling (CVS)

Amniocentesis and Chorionic Villus Sampling (CVS)

4.7.1 What is Amniocentesis?

Amniocentesis is a prenatal medical procedure used to diagnose chromosomal abnormalities and foetal infections. It involves extracting a small amount of amniotic fluid, which contains foetal cells, to analyse the DNA and chromosomes for any genetic disorders. Common disorders detected include Down syndrome, spina bifida, Edward syndrome, and Turner syndrome. The test can also assess the baby’s lung maturity and check for foetal infections. However, due to misuse for sex determination leading to female foeticide, the procedure is legally restricted in many regions, including India.

Why is Amniocentesis Performed?

Amniocentesis is primarily conducted to:

1. Assess Chromosomal Health: Check for abnormalities in the foetus’s karyotype, such as Down syndrome (Trisomy 21), Edward syndrome (Trisomy 18), and Turner syndrome (Monosomy X).
2. Detect Neural Tube Defects: Conditions like spina bifida can be diagnosed.
3. Test for Foetal Infections: Amniotic fluid can reveal if the foetus has been infected.
4. Determine Lung Maturity: It can assess whether the baby’s lungs are ready for birth, especially if early delivery is anticipated.

4.7.2 Procedure of Amniocentesis

1. Preparation: A local anaesthetic is administered to the mother to minimize pain.
2. Needle Insertion: Under ultrasound guidance, a needle is inserted through the mother’s abdomen and uterus into the amniotic sac.
3. Fluid Extraction: Approximately 20 ml of amniotic fluid is withdrawn.
4. Cell Culture: Foetal cells are separated, cultured, and examined under a microscope to identify chromosomal abnormalities.

4.7.3 Chromosomal Abnormalities Detected

Down syndrome (Trisomy 21): A condition where there is an extra chromosome 21, affecting brain and body development.

Edward syndrome (Trisomy 18): An additional chromosome 18 disrupts normal development, leading to life-threatening complications.

Turner syndrome (Monosomy X): A condition where a female is missing one X chromosome, leading to various physical and reproductive issues.

4.7.4 Risks and Legal Restrictions

While generally safe, the procedure carries some risks, including:

Miscarriage: Rare, but the most concerning risk.

Cramping: Mild discomfort may occur after the procedure.

Amniotic Fluid Leakage: Leakage from the puncture site or vagina can happen but is usually minimal.

Preterm Labor: There is a slight risk of inducing preterm labour.

Foetal Injuries: Though exceedingly rare due to ultrasound guidance, the needle could potentially injure the foetus.

Legal Restrictions: Ban on Amniocentesis for Sex Determination

In India, amniocentesis has been banned for sex determination under the Preconception and Prenatal Diagnostic Techniques Act (1994). The reason for the ban is the cultural preference for male children, leading to female foeticide. By using amniocentesis to determine the sex of the foetus, many female foetuses were being aborted. The legal restrictions aim to curb this practice and protect gender balance in society.

4.7.5 Chorionic Villus Sampling (CVS)

CVS is an alternative prenatal test to detect genetic disorders earlier in pregnancy. A small sample of chorionic villi is taken from the placenta, either through the cervix or abdomen, and tested for genetic problems. This test, like amniocentesis, can detect chromosomal abnormalities but is conducted earlier in the pregnancy.

4.7.6 Ethical and Population Concerns

While amniocentesis plays a crucial role in detecting genetic disorders and improving prenatal care, its misuse for non-medical purposes (like sex determination) raises significant ethical issues. The ban on sex determination using this method is part of broader efforts to address gender imbalances and protect the rights of the unborn child.