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Chorionic villus sampling is a prenatal diagnostic procedure performed between 10 and 13 weeks of gestation to detect genetic and chromosomal conditions. The procedure involves collecting a small sample of placental tissue (chorionic villi), which contains the same genetic material as the fetus. Chorionic villus sampling offers early, definitive results for conditions such as Down syndrome and other inherited disorders. The procedure can be performed either transabdominally or transcervically, depending on the location of the placenta. Chorionic villus sampling is typically recommended for individuals with increased risk, including abnormal screening results, advanced maternal age, or a family history of genetic conditions. Although generally safe, chorionic villus sampling carries a small risk of complications, including miscarriage, making informed patient counseling essential. As prenatal testing options evolve, chorionic villus sampling remains a valuable tool for early diagnosis and decision-making. This activity reviews the indications, contraindications, risks, techniques, and utility of the procedure. Participants gain insights into patient selection, risk assessment, counseling strategies, and potential complications. The activity also highlights the role of the interprofessional team in ensuring safe, informed, and coordinated prenatal care. Objectives: Differentiate between the transabdominal and transcervical approaches to chorionic villus sampling, including indications and associated risks. Identify common chromosomal abnormalities detected through chorionic villus sampling and their clinical significance. Implement evidence-based protocols for performing chorionic villus sampling. Collaborate with an interprofessional healthcare team to deliver comprehensive counseling and support informed, patient-centered decision-making. Access free multiple choice questions on this topic.

Chorionic villus sampling is a crucial tool in prenatal genetic diagnostic testing, typically performed between 10 and 13 weeks of gestation. Unlike screening tests, which estimate the risk of a genetic condition, chorionic villus sampling provides a definitive diagnosis by analyzing placental tissue for chromosomal abnormalities and specific genetic disorders. This early diagnostic capability is critical, as approximately 1 in 150 live births is affected by a chromosomal abnormality, and timely information can significantly impact the course of prenatal care.[1] One of the primary advantages of chorionic villus sampling is its ability to deliver diagnostic results weeks earlier than amniocentesis, which is typically performed after 15 weeks of gestation. This earlier timeline provides pregnant patients with critical information during the first trimester, when more options are available for clinical decision-making. Early diagnosis through chorionic villus sampling can inform decisions regarding the continuation or termination of pregnancy. If termination is considered, having results in the first trimester allows access to earlier and safer procedures, which carry fewer medical risks and are often associated with reduced emotional and psychological burden. Based on chorionic villus sampling results, patients may choose to seek further genetic counseling, plan for specialized obstetric management, or pursue early referrals to pediatric subspecialists who can assist in preparing for potential neonatal interventions or long-term care needs.

There are limited data directly comparing the risks of transcervical versus transabdominal chorionic villus sampling. However, current evidence does not suggest a significant difference in complication rates between the 2 approaches.[1][1] The risks associated with chorionic villus sampling are similar to those of amniocentesis and may include pregnancy loss, bleeding, infection, rupture of membranes, and uncertain results. The pregnancy loss rate has decreased with the use of ultrasound guidance and improvements in skill and technique. A systematic review of the complications of chorionic villus sampling found a total fetal loss of 0.7% within 14 days, 1.3% within 30 days, and 2% for loss anytime during pregnancy using a transabdominal approach. In the amniocentesis group, the total rate of fetal loss within 14 days was 0.6%.[8] A more recent cohort study found that pregnancy loss rates following chorionic villus sampling were comparable to those in pregnancies without chorionic villus sampling, confirming that the risk of this procedure is low.[9] Predictors of increased fetal loss include the number of times the needle or catheter is introduced, the experience and skill of the operator, pregnancies after assisted reproductive techniques, and the use of a transcervical cannula instead of biopsy forceps.[10][11] With chorionic villus sampling, there is a possibility of identifying confined placental mosaicism, which occurs in 1% to 2% of cases.[12] This possibility arises when there is a discrepancy between the chromosomal makeup of the placenta and that of the fetus. The fetus is truly mosaic in 10% of cases. Mosaicism identified by chorionic villus sampling should be followed by amniocentesis in the second trimester to determine the genetic makeup of the amniocytes, which contain fetal cells. The finding of mosaicism is associated with an increased risk of poor placental function and perinatal complications, including fetal growth restriction and maternal hypertension.[13]

Predictors of increased fetal loss include the number of times the needle or catheter is introduced, the experience and skill of the operator, pregnancies after assisted reproductive techniques, and the use of a transcervical cannula instead of biopsy forceps.[10][11] With chorionic villus sampling, there is a possibility of identifying confined placental mosaicism, which occurs in 1% to 2% of cases.[12] This possibility arises when there is a discrepancy between the chromosomal makeup of the placenta and that of the fetus. The fetus is truly mosaic in 10% of cases. Mosaicism identified by chorionic villus sampling should be followed by amniocentesis in the second trimester to determine the genetic makeup of the amniocytes, which contain fetal cells. The finding of mosaicism is associated with an increased risk of poor placental function and perinatal complications, including fetal growth restriction and maternal hypertension.[13] In addition, limb reduction defects and oromandibular hypogenesis have been described in the literature as potential risks associated with chorionic villus sampling.[14] Early chorionic villus sampling (before 10 weeks of gestation) has been identified as a risk factor for these complications. The World Health Organization estimates the risk of limb defects to be approximately 6 per 10,000, which is comparable to the risk in the general population.[1][15] Although the risk is low, it is essential to inform patients about the data when considering chorionic villus sampling before 10 weeks. Vaginal spotting has been reported in up to 32% of women and is more common after transcervical chorionic villus sampling.[1][16] The incidence of culture failure, leakage of amniotic fluid, or infection after chorionic villus sampling is reported to be less than 0.5%.

In addition, limb reduction defects and oromandibular hypogenesis have been described in the literature as potential risks associated with chorionic villus sampling.[14] Early chorionic villus sampling (before 10 weeks of gestation) has been identified as a risk factor for these complications. The World Health Organization estimates the risk of limb defects to be approximately 6 per 10,000, which is comparable to the risk in the general population.[1][15] Although the risk is low, it is essential to inform patients about the data when considering chorionic villus sampling before 10 weeks. Vaginal spotting has been reported in up to 32% of women and is more common after transcervical chorionic villus sampling.[1][16] The incidence of culture failure, leakage of amniotic fluid, or infection after chorionic villus sampling is reported to be less than 0.5%. When discussing genetic diagnostic testing in the setting of multiple gestations, counseling should include a thorough discussion of management options if only 1 fetus has aneuploidy. Such options include continuing the pregnancy, terminating the pregnancy, and selective second-trimester termination of the affected fetus.[1] There are limited data concerning the risk of fetal loss with chorionic villus sampling or amniocentesis in twin gestations. In a recent systematic review, the procedure-related loss rate for chorionic villus sampling and amniocentesis in twin pregnancies was estimated at 1%. With chorionic villus sampling, there is also a 1% chance for cross-contamination, or inadvertent sampling of both fetuses, which can lead to misinterpreted results.[17] In addition, the results from a recent multicenter study involving 8583 twin pregnancies showed that pregnancies undergoing chorionic villus sampling have a 2-fold increased risk of fetal loss before 24 weeks of gestation compared to those not undergoing chorionic villus sampling. This study also identified factors that provide an independent contribution to the increased risk of miscarriage or fetal loss in twin pregnancy. These factors include increased maternal weight, Black race, monochorionicity, monoamnionicity, large intertwin discordance in crown-rump length, and increased fetal nuchal translucency. After adjustment for maternal and pregnancy characteristics, the chorionic villus sampling procedure itself did not provide a significant contribution to the risk of fetal loss in twin pregnancies undergoing chorionic villus sampling, suggesting that the procedure itself is not the cause of the increased fetal loss risk.[18]

Effective performance of chorionic villus sampling requires a high level of skill, strategic planning, ethical decision-making, and interprofessional collaboration to ensure patient-centered care and optimal outcomes. Maternal-fetal medicine subspecialists must possess technical expertise in both transcervical and transabdominal approaches, applying careful procedural strategies guided by real-time ultrasound to minimize risk. Given the specific time frame in which chorionic villus sampling can be performed, early referral to maternal-fetal medicine is a key factor in ensuring patients have access to the procedure. Ethical responsibilities include ensuring informed consent through clear and compassionate communication about the risks, benefits, and alternatives, thereby allowing patients to make decisions that align with their values. Genetic counselors are an additional resource for families, helping them understand risks and options for prenatal testing. Nurses play a critical role in patient education, emotional support, and post-procedural care, whereas pharmacists contribute by reviewing medications such as anticoagulants that may affect procedural safety. Interprofessional communication facilitates the seamless exchange of clinical information and coordinated decision-making among maternal-fetal medicine subspecialists, genetic counselors, pediatric subspecialists, and primary obstetric providers. Effective care coordination ensures timely referrals, accurate specimen handling, and follow-up on results, all of which contribute to improved patient safety, satisfaction, and overall team performance. Through a shared commitment to collaboration and patient advocacy, healthcare teams can enhance the quality and effectiveness of prenatal diagnostic care involving chorionic villus sampling.