Answer
Amniocentesis and chorionic villus sapling (CVS) are two diagnostic procedures used during pregnancy to diagnose fetal abnormalities-- genetic diseases and chromosomal abnormalities.
Amniocentesis
Time: This procedure is usually performed between the 14th and 18th week of pregnancy.
Procedure: In amniocentesis a long needle attached to a syringe is passed through the pregnant woman's abdomen and guided by ultrasound into the amniotic sac. For testing, about 10 to 15 ml of amniotic fluid is withdrawn. The fluid is used for enzymatic and other chemical testing. The sloughed off fetal cells in the fluid are centrifuged down, collected and cultured in the lab . When enough cells have grown they are used for karyotyping and other microscopic studies.
CVS
Time: CVS samples can be collected as early as the eighth week of pregnant, but the 10th week is considered the optimal period.
Procedure: In this procedure a tube or a catheter is passed through the cervix through the vaginal canal and guided by ultra sound to come in contact with some villi of the chorion. Some of the chorionic cells are aspirated into the tube and these are used for chemical tests and karyotyping.
Work Step by Step
Diagnoses:
Amniocentesis;
Some fetal diseases and syndromes that have been diagnosed by amniocentesis are Down's
Syndrome, Klinefelter's Syndrome, sickle cell anemia, Tay Sach's disease, cystic fibrosis, and
spina bifida.
CVS.
The CVS procedure has been used to detect several fetal diseases and syndromes. These
include Duchenne Muscular Dystrophy, Down's Syndrome, Klinefelter's Syndrome, and cystic
fibrosis.
