Chorionic Villus Sampling

Invasive procedure to obtain chorionic villus tissue generally performed between 10 and 12 weeks of gestation. Procedural risk of fetal loss (higher than for amniocentesis): approximately 1%.

Use

Provides placental material for chromosome (cytogenetic) testing, biochemical testing (metabolic disorders/inborn errors of metabolism), and molecular DNA-based testing for inherited disease (e.g., cystic fibrosis, fragile X).

Primary advantage over amniocentesis is earlier time frame, allowing pregnancy termination in the first trimester or earlier relief of anxiety.

Limitations

Chromosome results may be ambiguous due to confined placental mosaicism (abnormal chromosome line limited to placental tissue) in approximately 2% of cases, requiring follow-up by amniocentesis

Maternal cell contamination must be avoided for accurate diagnosis based on fetal chromosomes, enzyme assay, or DNA analysis

Does not provide material to screen for neural tube defects