Chorionic Villus Sampling

Chapter 236 Chorionic Villus Sampling



DESCRIPTION


A technique for obtaining fetal chorionic villus cells for cytogenetic or other testing, chorionic villus sampling (CVS) is usually performed between 10 and 13 weeks’ gestation and involves aspiration of placental tissue using either percutaneous transabdominal or transcervical approaches. Transabdominal CVS can be performed at gestations greater than 13 weeks. A transvaginal approach similar to the transabdominal method has also been used for retroverted uteruses.



INDICATIONS


Genetic testing for fetal chromosome anomalies prompted by risk factors or an abnormal screening test result during the first trimester. (Neural tube defects in the fetus cannot be detected by CVS.)



CONTRAINDICATIONS


Thrombocytopenia or antiplatelet antibodies, active vaginal bleeding, or infection are relative contraindications. For transcervical CVS: cervical stenosis, cervical or lower uterine myomas. For transabdominal CVS: fetal position that blocks access to the placenta, known or suspected intra-abdominal adhesions that could block access to the uterus. CVS may be technically difficult to accomplish in patients with multiple gestations. The risk of human immunodeficiency virus (HIV) vertical transmission associated with early invasive diagnostic techniques is lower than previously expected (3%) and similar to women who do not undergo the procedure.



REQUIRED EQUIPMENT



• Skin (or vaginal) preparation materials (iodine-based antibacterial solution [e.g., Betadine] or other suitable cleansing agents)

• Sterile gloves

• Tissue transport medium (to be specified by the laboratory used and the test to be performed)

• Ultrasonography unit


For Transvaginal Approach



• Vaginal speculum

• Sponge stick (may be useful to atraumatically grasp and manipulate the cervix)

• Small (1.5-mm) aspiration cannula (with obturator) and 20- to 30-mL syringe; small biopsy forceps may be used as an alternative


For Transabdominal Approach



• 20- and 22-gauge spinal needles (or smaller), 20-cc syringe, three sterile 10-cc specimen tubes with caps (plain, without additive), sterile drape (one with a small fenestration or multiple drapes)

• If desired: 1% lidocaine without epinephrine, 5-cc syringe, 22-gauge needle (if not included in amniocentesis kit)


TECHNIQUE


The consensus is that CVS, both transabdominal and transcervical, must be performed under ultrasonographic control. Ultrasonography is performed before CVS to confirm the gestational age of the fetus. Ultrasonography can also document multiple gestations and whether the multiples share a single placenta or each has its own. (It is important to determine the number of placentas because each must be sampled separately to obtain an accurate genetic picture of each fetus.)

Related posts:

  1. Anemia
  2. Toxic Shock Syndrome
  3. Hysteroscopy
  4. Gingivitis in Pregnancy

Stay updated, free articles. Join our Telegram channel
Tags:
Jun 6, 2016 | Posted by in GYNECOLOGY | Comments Off on Chorionic Villus Sampling

Full access? Get Clinical Tree
Get Clinical Tree app for offline access