Prenatal testing is used to diagnose chromosomal abnormalities in the fetus. Here tissue sampling of the fetus is done and cytogenetic tests are done on these tissue. This can be done by 3 methods.

Chorionic Villus Sampling
Done when the pregnancy is above 10 - 12 weeks of age. A bit of the placenta is taken under ultrasound guidance.

Amniocentesis

Done during 15 - 18 weeks of pregnancy. Here a small amount of fluid around the fetus is taken under ultrasound guidance.

Cordocentesis

After 18 weeks of pregnancy, a blood sample of the fetus is taken for cytogenetic testing.

Who needs prenatal testing

	Mother's age more than 35. Such mothers have an increased risk of bearing babies with chromosomal defects.
	Previous pregnancy with malformed baby.
	Family history of congenital diseases.
	Recurrent pregnancy losses.
	Mothers with illness like diabetes, congenital heart diseases, epilepsy and exposure to drugs and chemicals during early pregnancy.
	Parents who are consanguinous. (close relatives)