Chorionic Villus Sampling (CVS)
Chorionic Villus Sampling (CVS) is a diagnostic test performed at Melbourne Ultrasound for Women, involving the extraction of a small tissue sample known as "chorionic villi" from the developing placenta of expectant mothers.
The placenta typically shares genetic characteristics with the fetus, allowing for the detection of chromosomal or DNA abnormalities like Down syndrome.
At Melbourne Ultrasound for Women, our dedicated specialized Obstetrician Gynaecologist possesses extensive expertise in administering CVS for pregnant individuals.
Who is offered a CVS?
Most CVS testing is recommended for pregnant women with specific risks of chromosomal abnormalities, such as Down syndrome. This may encompass:
Women who have exhibited an elevated probability of a chromosome-related condition through cell-free fetal DNA testing (NIPT).
Women who have displayed an elevated likelihood on a nuchal translucency test.
Women aged 35 and older.
Women who have previously experienced a pregnancy affected by a chromosomal abnormality.
Parents known to carry a chromosomal abnormality themselves.
Parents known to be carriers of genetic disorders.
Parents at risk of having a baby with one or multiple rare "metabolic" disorders.
In some instances, CVS might be conducted for women particularly concerned about the risk of chromosomal abnormalities.
Trans-abdominal CVS
The sampling process entails utilizing a needle inserted through the abdominal wall, known as trans-abdominal CVS. A delicate needle is guided through the skin and into the uterus to the placental edge, its trajectory meticulously monitored on the ultrasound display. A finer needle is subsequently introduced through the outer needle and into the placental tissue.
Using a syringe, minute fragments of placental tissue are drawn up for extraction. The obtained tissue is evaluated to ensure its adequacy, and if necessary, additional aspirations are carried out through the inner needle without causing any extra discomfort. It is important to note that the needle is never introduced into the amniotic sac at any point during the procedure, which serves to minimize test-related risks, and any fetal movements that occur during the procedure are not a cause for concern.
How is CVS performed?
Trans-cervical CVS
Should your scan reveal that the placenta is developing at the rear uterine wall and positioned low in the uterus, it might facilitate your obstetrician in conducting the CVS procedure trans-cervically, where a speculum is introduced into the vagina and the cervix is cleansed with an antiseptic solution; subsequently, a specialized catheter is carefully navigated into the placenta aided by ultrasound, allowing for the gentle aspiration of placental tissue.
Usually this trans-cervical CVS procedure is entirely painless, and a minor amount of bleeding is relatively frequent; the accompanying image illustrates the catheter's passage through the cervix and into the placenta situated on the back wall of the uterus.
When is CVS carried out?
Ideally, the CVS test is recommended during the 11-13 week gestation period. However, it can be performed as early as 10 weeks and up to 40 weeks if necessary.
Preparation Guidelines for Your Appointment
Having knowledge of your blood group, especially your Rhesus (Rh) status, is vital prior to a CVS test. If possible, kindly request this information from your referring doctor or bring your blood group card to your Melbourne Ultrasound for Women appointment
Please be aware, if you possess a Rhesus negative blood group, you will need an anti-D injection after the CVS.
Our proficient Melbourne Ultrasound for Women Obstetrician will provide you with comprehensive information about this during your CVS appointment.
When you come in for your CVS appointment at Melbourne Ultrasound for Women, having a moderately full bladder is beneficial.
This positioning elevates the uterus into the abdominal cavity, simplifying access to the placenta for the procedure. If, however, you find the full bladder uncomfortable, our skilled team will guide you to partially empty your bladder if needed.
What is done with the cells?
The cells obtained at CVS are sent to Victorian Clinical Genetic Services (VCGS) and are allowed to grow in the laboratory until there are enough for testing the chromosomes.
Each of the chromosomes is carefully examined to check that there are the correct number and that the appearance and length of each chromosome is normal. If the fetus has Down Syndrome then there is an additional chromosome 21 present. The sex of the fetus can also be determined by looking at the chromosomes - you can find this out if you ask your doctor.
The laboratory will usually have the result available within 2 weeks. Your doctor will be informed and he or she will pass it on to you. If you wish, an extra test, called FISH, can be carried out to tell you within 2 working days if Down Syndrome is present. The laboratory charges extra for FISH testing.
Understanding test risks
CVS is a well-established diagnostic procedure. As with any invasive procedure, there is a small risk of complications.
Based on Dr Victor Hurley's published experience, including results from another experienced operator, the miscarriage rate following CVS was not demonstrably higher than in comparable pregnancies where no procedure was performed. The procedure-related risk of miscarriage is therefore considered to be very low, with a best estimate of 1 in 200 (0.5%) or less.
A small number of women may experience light vaginal spotting or mild cramping following the procedure. These symptoms are usually short-lived and do not affect the pregnancy.
If your blood group is Rh negative, you will usually be offered an Anti-D injection following the procedure.
Direct injury to the baby from the needle is exceptionally rare, as the procedure is performed under continuous ultrasound guidance. Serious complications affecting either the mother or baby are also very uncommon.
Occasionally, the laboratory may be unable to obtain sufficient information from the sample, and a repeat procedure may be recommended. Diagnostic results are highly accurate, although very rarely an uncertain result may require additional testing.
Post CVS care guidelines
Following your CVS procedure, we recommend that you rest for the remainder of the day. Bed rest is not required, but you should avoid strenuous exercise, heavy lifting and other vigorous activities. If you feel well enough, you may return to work the following day unless otherwise advised by your doctor.
It is common to experience mild cramping, lower abdominal discomfort or soreness once the local anaesthetic wears off. Some women may also notice a small amount of vaginal spotting following the procedure. These symptoms are expected and do not usually indicate a problem.
You will remain with us for a 10–15 minute recovery period after your procedure before going home. Although most women are able to drive themselves home, many find it reassuring to have someone accompany them.
Please contact us or seek urgent medical attention if you experience:
Heavy vaginal bleeding
Severe or worsening abdominal pain
Fever or chills
Leakage of fluid from the vagina
Feeling generally unwell
When are you informed of the CVS results?
Dr Hurley will ring you with the CVS results as soon as they become available, and we also forward them to your referring doctor.
Fast FISH results are available in 24-48 hours. The full karyotype usually takes 10-14 days; microarrays usually take 5-10 days, and our team will call with all of your results whether they are normal or not.
