Beginning in 1968, cells from amniotic fluid could be analyzed for chromosome disorders like Down's syndrome. Today, amniocentesis permits the diagnosis of a wide range of disorders. Amniocentesis is normally recommended after sixteen weeks of pregnancy. Test results are usually available to the patient in around three weeks . Cells from the fetus will be floating in this fluid, and can be separated and tested. Miscarriage risk of amniocentesis is commonly quoted as 0.5% (1:200).   quoted as 0.5% (1:200).

Chorionic villus sampling is when samples of fetal tissue is retrieved from the fetus. The samples are then analyzed for chromosomal, biochemical, and DNA content.  Ultrasound-guided CVS is now widely used. It can be performed much earlier in pregnancy than amniocentesis .  The test is carried out after 11 weeks of pregnancy. The collecting of the chorionic villi is carried out crossing the abdominal wall with a special needle.  

This procedure is also called cordocentesis, or percutaneous umbilical blood sampling (PUBS). Fetal blood sampling is done as a part of diagnosing, treating, and monitoring fetal problems at various times during pregnancy. A fetal blood sample may be taken to: diagnose genetic or chromo-some abnormalities check for and treat severe fetal anemia or other blood problems such as Rh disease check for fetal infection give certain medications to the fetus.

There are several ways blood can be obtained from the fetus. After cleansing the mother’s abdomen with antiseptic, a long, thin needle is inserted into the mother’s uterus guided by ultrasound. Blood may be taken from the following sources: blood vessels of the umbilical cord (also called cordocentesis, or percutaneous umbilical blood sampling, or PUBS) a fetal blood vessel, usually in the liver or heart.