Amniocentesis is a medical procedure used primarily in prenatal diagnosis of chromosomal abnormalities and fetal infections as well as for sex determination. In this procedure, a small amount of amniotic fluid, which contains fetal tissues, is sampled from the amniotic sac surrounding a developing fetus.

Amniocentesis can be done for various reasons:
1. Genetic testing. Genetic amniocentesis involves taking a sample of amniotic fluid and testing it for certain conditions, such as Down syndrome.
2. Fetal lung testing. Fetal lung maturity testing involves taking a sample of amniotic fluid and testing it to determine whether the baby's lungs are mature enough for birth.
3. Diagnosis of fetal infection. Occasionally, amniocentesis is used to evaluate a baby for infection or other illness. The procedure also can be done to evaluate the severity of anemia in babies who have Rh sensitization - an uncommon condition in which a mother's immune system produces antibodies against a specific protein on the surface of the baby's blood cells.
4. Treatment. If you accumulate too much amniotic fluid during pregnancy (polyhydramnios), amniocentesis might be done to drain excess amniotic fluid from your uterus

Chorionic Villus Sampling (CVS) is a prenatal test in which a sample of chorionic villi is removed from the placenta for testing. During pregnancy, the placenta provides oxygen and nutrients to the growing baby and removes waste products from the baby's blood.

Not everyone who is pregnant will need to have chorionic villus sampling. It is usually performed when there is a possibility that the baby may have an abnormal condition. Your doctor may consider chorionic villus sampling if:
1. You are over 35 years of age-women over 35 are at higher risk of having children with chromosomal abnormalities.
2. You or your partner has a genetic disorder.
3. You or your partner has a family history of a genetic disorder.
4. You have had other children with genetic or biochemical disorders.
5. You have had spontaneous abortions.
6. You have had prenatal screening tests with abnormal results.

Thalassemia is a blood disorder passed down through families (inherited) in which the body makes an abnormal form of hemoglobin, the protein in red blood cells that carries oxygen. The disorder results in excessive destruction of red blood cells, which leads to anemia. Anemia is a disorder in which your body doesn't have enough normal, healthy red blood cells (RBC).
This disease is inherited, meaning that at least one of your parents must be a carrier of the disease. It is caused by either a genetic mutation, or a deletion of certain key genes.
The two main forms of thalassemia are alpha thalassemia and beta thalassemia. In alpha thalassemia, at least one of the alpha globin genes has a mutation or abnormality. In beta thalassemia, the beta globin genes are the ones affected.
Each of these two forms of thalassemia has several distinct types. The exact form you have will affect the severity of your symptoms and your prognosis.