First Trimester: Chorionic Villus Sampling
Between the tenth and twelfth week, a chorionic villus sampling (CVS) procedure can be performed in which either a needle inserted through the woman’s abdomen or a tube inserted through the woman’s vagina and cervix is used to obtain a tissue sample from the placenta. These cells have the same genetic makeup as the fetus and are analyzed for chromosomal disorders, such as is seen in Down syndrome, and gene abnormalities that cause metabolic disorders, such as Tay-Sachs and cystic fibrosis.
Any of the following are the usual indications for this diagnostic procedure:
- An earlier screening test gives a reason for concern
- The pregnant woman is 35 years of age or older
- There is a strong family history of a specific genetic disorder (in either biological parent)
- Both biological parents possess a gene for an inherited disorder
- A previous child of one of the biological parents had a birth defect
Carefully chosen screening tests may help the woman avoid this diagnostic procedure, which is associated with a risk of miscarriage and infection.