Everything About Chorionic Villus Sampling: A Complete Parent’s Manual

Chorionic Villus Sampling is a prenatal diagnostic test that is offered to a pregnant woman between 10 and 13 weeks of pregnancy to detect the presence of any genetic abnormalities of the fetus, like Down’s syndrome, Edwards’ syndrome, or Patau’s syndrome ¹. It is done by obtaining and testing a sample of the cells obtained from the placenta, known as Chorionic villus ².

Chorionic Villus Sampling has been determined as the only safe invasive prenatal diagnostic procedure before the 14th week of gestation ³. Earlier diagnosis using Chorionic Villus sampling at the first trimester, provides earlier psychological and medical advantage to the expecting mother ⁴

This article covers what CVS is, how the procedure works, what it can detect, how accurate it is, and whether it carries any real risk.

What Is Chorionic Villus Sampling? Meaning and Overview

“Chorionic villus” refers to the tiny finger-like projections that protrude out of the placenta, which are derived from the same zygotic origin as the fetus, containing the same chromosomes as the fetus ⁵. It’s a medical procedure that involves retrieving these cells from the placenta for laboratory procedures. This can detect whether a chromosome is missing or abnormal ^{6 7}.

While it may not be done as a routine procedure, it is typically recommended for those who receive an “increased risk” result from a Non-Invasive Prenatal Test (NIPT) or other screening methods. Because screenings like NIPT only provide a statistical probability of a condition, chorionic villus sampling acts as a definitive diagnostic tool to confirm or rule out those results. It is also suggested for individuals with a relevant family history or those who have had a previous pregnancy affected by a genetic condition.⁸

Chorionic Villus Sampling Procedure

The chorionic villus sampling procedure is usually performed between 11⁺⁰ and 13⁺⁶ weeks of gestation ⁸.  The time period ensures minimization of early pregnancy complications while ensuring the results arrive by the first trimester ⁹.

It is done precisely using specialized equipment under continuous real-time ultrasound guidance to ensure the quality of the sample collected. Based on the location of the sample collected, it may be of two types, namely.

• Transabdominal CVS: A thin needle is guided through the abdomen and uterine wall. A syringe attached to the needle collects the sample. This is currently the most prevalent technique ¹⁰
• Transcervical CVS: A thin, flexible tube or small forceps are passed through the vagina and cervix under ultrasound ¹⁰

The entire procedure is completed within 10 minutes. The results may be obtained within 3 days in a rapid test, while a more detailed test may take up to 2-3 weeks. The procedure is generally well tolerated, though mild cramping or discomfort may occur afterwards.

What Is the Purpose of Chorionic Villus Sampling?

While many prenatal tests are limited to screening, chorionic villus sampling provides the definitive diagnostic data needed to confirm the presence of chromosomal or genetic conditions.¹ It is typically recommended in the following situations:

1. When there is a known family history of genetic disorders
2. When the maternal age is above 35 years
3. If a prior screening test has indicated potential abnormalities
4. When one or both parents are carriers of inherited conditions such as cystic fibrosis or sickle cell anaemia identified through a carrier screening test
5. If a previous pregnancy was affected by a genetic condition
6. When there is a history of a child born with genetic defects ¹¹

What Does Chorionic Villus Sampling Detect and What Is It Used For?

Chorionic villus sampling provides information regarding chromosomal health and specific inherited diseases.

It includes the identification of:

• Chromosomal abnormalities: Down’s syndrome (Trisomy 21), Edward’s syndrome (Trisomy 18), and Patau’s syndrome (Trisomy 13)
• Inherited genetic disorders: Cystic fibrosis, Sickle cell anemia, Thalassaemia, Muscular dystrophy, and Tay-Sachs disease ¹²

Though it is an effective method to detect congenital defects, the test is unable to detect spine defects like spina bifida, which may require alternative tests like blood screening and ultrasound ¹¹

How Accurate Is Chorionic Villus Sampling?

A primary consideration for most families is how accurate chorionic villus sampling is. The CVS testing is found to be about 99% accurate, although inaccuracies may occur when the samples are not properly collected¹¹. The success rate of the samples obtained is about 99% for both techniques, where about 96% of the cases obtain an adequate amount of chorionic cells during the first attempt¹³. One of the methods to ensure accurate results is to perform a genetic test called maternal cell contamination testing. This helps confirm that the sample obtained is of fetal origin.

Is Chorionic Villus Sampling Dangerous or Diagnostic?

While all invasive procedures involve some degree of risk, CVS is generally considered safe when performed by skilled operators. CVS can cause

1. Miscarriage
2. Infection.
3. Bleeding.
4. Rh sensitization
5. Oromandibular-limb hypogenesis ⁶

However, CVS has some limitations:

• It is not possible to detect the presence of neural tube defects like Spina bifida because different screening techniques are required for their detection.
• There may be some rare laboratory or biological factors (like mosaicism) that may require further testing.
• The test can detect the presence of genetic abnormalities, but it is not possible to determine the severity of the condition. ¹¹

Conclusion

Chorionic villus sampling remains a cornerstone of early genetic diagnosis, providing high accuracy and definitive answers for families at increased risk. While the decision to undergo an invasive procedure is a very personal one, the information that CVS can provide can be invaluable in clinical planning and for your own peace of mind.

If you are contemplating this procedure, talking to a healthcare professional about the advantages and disadvantages can help you make an informed decision for your pregnancy. State-of-the-art screening tests and counseling services are available to assist you in all aspects of this diagnostic process.

FAQs

1. At what stage of pregnancy is chorionic villus sampling performed?
   The procedure is carried out early in pregnancy, between the 10th and 14th weeks of pregnancy
2. Is chorionic villus sampling a diagnostic or screening test?
   It is a diagnostic procedure, meaning that in almost all cases, it can tell for sure whether a child has a specific chromosome disorder or not
3. What genetic conditions can chorionic villus sampling detect?
   It can detect nearly all chromosomal abnormalities, such as Down syndrome and several hundred genetic disorders, such as cystic fibrosis and sickle cell anemia.
4. Are there risks associated with chorionic villus sampling?
   Yes, since CVS is an invasive procedure, there is a small risk of miscarriage, estimated at less than 0.5% in most experienced centers. There is also a small chance of infection and Rh sensitization.
5. How is CVS different from amniocentesis?
   The main differences between CVS and amniocentesis are that CVS is performed earlier in pregnancy (10-14 weeks) and a placental tissue sample is taken, while amniocentesis is performed later in pregnancy (after 16 weeks) and a sample of amniotic fluid is taken. Another difference is that amniocentesis can also pick up neural tube defects.

References:

1. Taylor M. Jones and Freddy J. Montero, “Chorionic Villus Sampling,” StatPearls – NCBI Bookshelf, April 26, 2025, https://www.ncbi.nlm.nih.gov/books/NBK563301/
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3. Ronald J. Wapner, “Invasive Prenatal Diagnostic Techniques,” Seminars in Perinatology 29, no. 6 (December 1, 2005): 401–4, https://doi.org/10.1053/j.semperi.2006.01.003.
4. Centers for Disease Control and Prevention. “Chorionic Villus Sampling and Amniocentesis: Recommendations for Prenatal Counseling,” July 21, 1995, https://www.cdc.gov/mmwr/preview/mmwrhtml/00038393.htm.
5. Johns Hopkins Medicine. “Chorionic Villus Sampling (CVS).” Johns Hopkins Medicine, 2023. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/chorionic-villus-sampling-cvs.
6. “Chorionic Villus Sampling (CVS),” n.d., https://medlineplus.gov/lab-tests/chorionic-villus-sampling-cvs/.
7. Zarko Alfirevic, Kate Navaratnam, and Faris Mujezinovic, “Amniocentesis and Chorionic Villus Sampling for Prenatal Diagnosis,” Cochrane Database of Systematic Reviews 2017, no. 9 (September 4, 2017): CD003252, https://doi.org/10.1002/14651858.cd003252.pub2.
8. “Amniocentesis and Chorionic Villus Sampling (Green-top Guideline No. 8) | RCOG,” RCOG, n.d., https://www.rcog.org.uk/guidance/browse-all-guidance/green-top-guidelines/amniocentesis-and-chorionic-villus-sampling-green-top-guideline-no-8/.
9. Ronald J. Wapner, “CHORIONIC VILLUS SAMPLING,” Obstetrics and Gynecology Clinics of North America 24, no. 1 (March 1, 1997): 83–110, https://doi.org/10.1016/s0889-8545(05)70291-6.
10. NHS Website, “What Happens,” nhs.uk, December 9, 2025, https://www.nhs.uk/tests-and-treatments/chorionic-villus-sampling-cvs/what-happens/.
11. Cleveland Clinic. “Chorionic Villus Sampling (CVS): What It Is, Benefits & Risks.” Cleveland Clinic, June 27, 2021. https://my.clevelandclinic.org/health/diagnostics/4028-chorionic-villus-sampling-for-prenatal-diagnosis.
12. Editor, “Chorionic Villus Sampling: CVS,” American Pregnancy Association, December 9, 2021, https://americanpregnancy.org/prenatal-testing/chorionic-villus-sampling/.
13. Brambati, B., L. Tului, A. Lanzani, G. Simoni, and T. Smidt-Jensen. “Transabdominal and Transcervical Chorionic Villus Sampling: Efficiency and Risk Evaluation of 2,411 Cases.” American Journal of Medical Genetics 35, no. 2 (February 1990): 160–64. https://doi.org/10.1002/ajmg.1320350204.