Chorionic Villus Sampling (CVS) is a prenatal diagnostic technique used for pregnant women suspected of carrying genetic disorders. This procedure involves extracting placental villus tissue for genetic analysis, allowing detection of chromosomal abnormalities or inherited diseases early in pregnancy (around 10 to 13 weeks). CVS provides more definitive diagnostic results compared to traditional serum screening, making it an essential screening tool for high-risk pregnancies.
This technique primarily targets chromosomal disorders such as Down syndrome and Edwards syndrome, as well as hereditary diseases like cystic fibrosis or Duchenne muscular dystrophy. Its core value lies in providing early diagnostic information to assist families in subsequent medical planning or psychological preparation.
CVS can be performed via transcervical or transabdominal approaches, both under ultrasound guidance. The physician uses a fine needle to puncture the uterine wall or through the cervix to extract a small amount of villus tissue, which contains the same genetic information as the fetus.
After obtaining the tissue, cell culture and chromosomal analysis are conducted to detect numerical abnormalities (such as trisomy), structural abnormalities, or specific gene defects. The genetic analysis accuracy can reach up to 99%, though potential limitations include tissue contamination or culture failure.
The procedure is mainly suitable for high-risk groups such as:
It is also used to determine fetal sex for diagnosing sex-linked diseases (e.g., Duchenne muscular dystrophy) or to confirm structural abnormalities such as microdeletions or microduplications.
The procedure usually takes about 15-30 minutes and is performed under painless conditions. Transcervical approach involves disinfecting the cervix and using a catheter to extract tissue, while transabdominal approach requires local anesthesia and puncture. Approximately 20-30 milligrams of tissue are collected, sufficient for genetic analysis.
Ultrasound localization is necessary before the procedure, and conditions such as uterine abnormalities or placental position are checked. Post-procedure observation lasts about 2 hours; some pregnant women may experience minor bleeding, which is normal. Results are typically available within 1-2 weeks, with expedited processing available in urgent cases.
Main advantages include:
Compared to non-invasive testing (NIPT), CVS provides definitive diagnosis, especially valuable for structural chromosomal abnormalities and single-gene disorders. In some cases, it can be combined with genetic counseling for family risk assessment.
Main risks include:
Serious complications include amniotic fluid leakage or fetal injury, with rare cases potentially leading to limb defects (incidence approximately 0.1-0.3%). The risk may increase in older pregnant women or those with uterine abnormalities, requiring detailed discussion with the physician regarding benefits and risks.
Contraindications include:
Pre-procedure assessments include measuring cervical length and placental location; gestational age should be between 10 and 13 weeks. After the procedure, avoid vigorous activity for 24 hours. If persistent bleeding or abdominal pain occurs, seek medical attention immediately.
CVS results may influence subsequent treatments:
Compared to other invasive tests, CVS and amniocentesis have similar complication risks, but the latter is performed later (15-20 weeks). When combined with genetic counseling, be aware of the timing differences in report interpretation.
Clinical studies show CVS detects 99% of Down syndrome cases, with a false-positive rate below 2%. Large-scale follow-up studies indicate its diagnostic accuracy surpasses traditional serum screening, though the miscarriage risk increases by 0.5-1%.
Newer techniques such as array comparative genomic hybridization (aCGH) have been integrated into CVS analysis, enabling detection of smaller chromosomal structural abnormalities. Many European and American countries list it as a first-line diagnostic tool for high-risk pregnancies.
Main alternatives include:
The non-invasive nature of NIPT makes it an initial screening option, but for definitive diagnosis or testing specific genetic disorders, CVS remains irreplaceable. Physicians will recommend the most suitable method based on gestational age and risk level.
What preparations are needed before undergoing chorionic villus sampling?
Before the procedure, the doctor usually arranges an ultrasound to confirm fetal position and amniotic fluid volume, and recommends fasting for 4 to 6 hours to reduce nausea risk. Additionally, avoid vigorous exercise before the procedure and inform the doctor if there is a history of bleeding tendency or uterine abnormalities.
Is bleeding or abdominal pain after CVS normal? How should it be managed?
Minor bleeding or lower abdominal discomfort are common and usually resolve within 24 to 48 hours. If bleeding exceeds one pad per hour, persistent severe abdominal pain, or fever occurs, seek medical attention immediately. Bed rest and abstaining from sexual activity for at least one week may be advised by the doctor.
When can normal activities and work resume after the procedure?
Most patients can walk slowly after 6 to 8 hours, but should avoid heavy lifting or standing for 24 hours. If the job is light, recovery typically occurs within three days; however, strenuous activities should be avoided for at least one week, following specific instructions from the doctor.
What is the difference in accuracy between chorionic villus sampling and amniocentesis?
CVS can be performed between 10 and 13 weeks of pregnancy, earlier than amniocentesis, but has a false-positive rate of about 1-3% for chromosomal abnormalities. Amniocentesis has an accuracy of 99% but is performed after 16 weeks. The choice depends on the timing and scope of genetic testing based on fetal risk assessment.
What follow-up should be taken if abnormal results are obtained?
If chromosomal abnormalities are detected, confirmatory tests such as amniocentesis or non-invasive chromosomal screening (NIPT) are recommended to verify results. Monitoring of uterine contractions and fetal development is also necessary. Genetic counselors will provide detailed risk analysis and subsequent medical planning.
%201.svg)
Copyright © 2025 MedFrontiers. All Rights Reserved.
