Chorionic Villus Sampling (CVS)
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Maternity
Chorionic Villus Sampling (CVS)
Fetal Medicine Unit
Introduction
Every year women have a CVS performed. Not all women need it, but for the ones
that do, it means putting themselves and their pregnancy on hold for what might
seem a lifetime.
The purpose of this booklet is to provide you with the facts and information about
CVS so that you and/or your partner will know what to expect from this test. The at
back of this booklet there is a small section of medical terms that you may find helpful
and there are pages for you to jot down questions which you might like to ask at your
visit.
We would be very grateful to hear your views and comments about your care on the
FMU (Fetal Medicine Unit). If you wish to have any further information contact:
Specialist Midwife
Fetal Medicine Unit
Liverpool Women’s Hospital
Crown Street
Liverpool
L8 7SS
Tel: 0151 702 4072
Appointments
When you attend for your appointment please report to the FMU reception desk.
This can be found on the ground floor opposite the Antenatal Clinic
Staff in the FMU
Who will you meet?
Consultants in Fetal and Maternal Medicine
Specialist Midwives
Health Care Assistant.
1Other staff you may meet
Several other people are involved with your care on the unit and each one has a very
important role.
If you have a query about your appointment please do not hesitate to contact the
FMU on 0151 702 4072. The consultants on the unit work with senior registrars who
are training in fetal medicine and during your visit you will meet them. Sometimes
student midwives and medical students will join them. If you have any concerns
about them being present, please let us know.
What is CVS?
CVS means the removal of the ‘finger-like projections which surround the embryonic
sac in early pregnancy. Their function is to form the placenta. A small amount of villi
are removed which causes no harm to the baby. This will allow both a direct culture
and a long term culture to be established. It can be performed as early as 11 weeks.
Benefits of having CVS
There are many reasons for having a CVS performed. However, the most common
reason is to detect whether a baby has a chromosomal or genetic disorder. The
intended benefit of having a CVS is that you will be informed as to whether the
baby’s chromosomes are normal or not. The benefit of having CVS is that it can be
performed early in the pregnancy, i.e. 11-13 weeks into the pregnancy.
What alternative do I have?
Alternatively amniocentesis (see separate leaflet) can be performed at approximately
16 weeks into the pregnancy. You may choose not to have any invasive test and
wait for the baby to be born.
Does having a CVS hurt?
Women frequently ask this question. Everybody’s threshold of pain is different. It is
true to say however that most women find the test ‘uncomfortable’. Some say it is
like having a blood test.
How is the test done?
The abdominal route
This is the usual route taken. You don’t necessarily need to have a full bladder. The
doctor will first perform an ultrasound scan to measure your baby and find where the
placenta (afterbirth) is situated. Before the test your skin is cleaned with antiseptic
wipes and then the procedure begins. Local anaesthetic is used to numb the skin.
2A sterile plastic pot containing pink liquid to transport the tissue to the laboratory is
labelled with your name, date of birth, address and hospital number. The details are
checked with you.
Ultrasound is used to see the needle and guide it into the placenta through your
tummy. The sample is obtained with a gentle suction and movement technique. The
doctor will check the sample under a microscope. If there is not enough then he will
take some more tissue.
The Transcervical route
This route is used occasionally when the abdominal route is not accessible. This
method is very similar to have a smear and isn’t too uncomfortable. First an
ultrasound scan is performed to locate the position of the placenta. After this you will
lie flat on your back with your knees apart. To help reduce the risk of infection, the
doctor will clean inside and around the vaginal area with antiseptic. Then a
speculum, a very small metal object that holds the vaginal walls apart, is inserted into
the vaginal so that the next of your womb (cervix) can be seen. Next a fine plastic
tube is placed into the vagina and cervix to take a sample of the placenta. On
reaching the placenta small pieces are gently sucked out with a syringe. The plastic
tube is taken out and the sample looked at under a microscope. If there is
insufficient tissue, the test is repeated. When the test is finished, the sample us sent
to the laboratory.
Your Sample
This will be looked at by the Regional Genetics Laboratory. The tissue is broken into
single cells. The cells are grown in culture and then looked at by one member of the
team and checked by another Senior Scientist. The result is interpreted and a report
faxed to the FMU. The slides from the sample will be stored as an internal quality
control measure until after the baby is born. In rare circumstances, where the
consultants feel it is necessary the cells may be stored longer. Otherwise, following
investigation, the tissue will be disposed of in accordance with health and safety. If a
DNA test for a specific genetic disorder is required, DNA will be prepared from the
3tissue and the appropriate tests carried out. The results will be checked by a Clinical
Scientist and a report will be faxed to the FMU or Clinical Genetics Department.
DNA from the sample will be stored in the laboratory for 10 years for quality
assurance purposes and may be used as a cross reference for future pregnancies.
How long do the results take?
For chromosomal analysis
In the majority of cases a rapid preliminary test called QF-PCR is performed on the
genetic material (DNA) from the sample. This detects 80% of all chromosome
abnormalities (Downs, Edwards and Patau syndromes and sex chromosomes
abnormalities). The results should be available within 4 working days.
In order to look for any remaining detectable abnormalities, cells from your sample
will be grown in culture and slides prepared. The results from this test will be
available within 3 weeks from having the CVS. There are some genetic or
chromosomal conditions that cannot be detected by these texts.
The slides from this sample will be stored as an internal quality control measure for 5
years.
Otherwise, following investigation, the cells will be disposed if in accordance with
health and safety.
For specific genetic condition
The length of time will vary according to the required test.
Possible complications
Here at the Liverpool Women’s NHS Foundation Trust, the chance of a miscarriage
following a CVS is similar to amniocentesis (0.5 - 1%, < 1 in 100). It can be difficult
to say whether a miscarriage is due to the test or would have happened anyway.
Other possible causes can be infection, the waters breaking, and the womb
becoming irritable.
Reliability
CVS is 98% reliable for diagnosing chromosomal abnormalities with only a small
change of a wrong result. DNA based tests are more than 99% reliable.
Culture failure
This occurs in 1% of cases and can either be due to: Fetal cells not growing; fetal
cells that start to grow and then stop; a different type of cell growth (mosaicism); or
maternal cells growing instead.
4In any of these situations you will be contacted and told of the problem and several
options will be discussed with you.
These are:
Have CVS again
Have an amniocentesis
Do nothing at all
CVS Results: The results are sent to the FMU by fax.
Rapid Test Results: You will be asked how you wish to receive them.
Full culture tests: The specialist midwife will inform you of the preliminary results
(PCR) by telephone and if the final results are normal we will contact you by 1st
class letter. If the results are abnormal we will contact you by phone as it is
necessary to speak to you as soon as possible to discuss the result in depth.
Culture Failure
The Specialist Midwife will notify you by telephone to discuss the matter. You may
want another test and so another appointment can be arranged for you.
Some general advice
After the test you will be taken to a counselling room to rest before going home.
Take things easy for the next couple of days and try to avoid household chores that
involve lifting, bending and stretching. Some ladies experience lower abdominal
discomfort within the 24 – 48 hours following the procedure. This can be expected
because of the procedure and can be relieved by taking Paracetamol.
If you experience any of the following symptoms you should contact the Gynaecology
Emergency Room at Liverpool Women’s Hospital or your referring hospital for further
advice.
Vaginal spotting of blood/bleeding like a period
Develop a temperature
Feel unwell
Loss of fluid from the vagina.
5Support Groups and useful addresses
The Alder Centre Down’s Syndrome Association
Alder Hey Children’s Hospital 155 Mitcham Road
Eaton Road London
Liverpool SW17 9BR
L12 2AP CLAPA (Cleft Lip and Palate
Tel Daytime: 0151 228 4811 Association)
Tel Daytime: 0151 228 4811 Dental Department
Tel Evening: 0151 288 9759 The Hospital for Sick Children
(19:00 – 22:00 hrs) Great Ormond Street
Offers support and understanding London
to anyone who has experienced WC1 0EP
the death of a child. Tel: 0171 388 1382
The Miscarriage Association SANDS (Stillbirth and Neonatal Death
c/o Clayton Hospital Society)
Northgate 28 Portland Place
Wakefield London
West Yorkshire W1 4DE
WF1 3JS Tel: 0171 436 5881
Tel: 01924 200799
CRUSE (Care for the Bereaved) ARC (Antenatal Results and Choices)
Cruse House 73-75 Charlotte Street
126 Sheen Road London
Richmond W1 1LB
Surrey Tel: 0207 631 0285
TW9 1UR
Tel: 0181 940 4818
Medical Glossary
Some common terms used in this booklet.
Fetus – The developing baby in the womb.
Chromosomes – Thread-like structures in a cell which carry the blueprint or genes
that give people their characteristics.
Gene – A single unit of inherited characteristic situated in a chromosome.
Placenta – Also known as the ‘afterbirth’, this is a unique organ in the womb that
supplies the baby with nourishment and the removal of waste products.
6Amniotic fluid – Also called liquor, this is the fluid that surrounds the baby.
Amniocentesis – Puncture of the amniotic sac and the removal of the fluid from
around the developing baby for testing.
Ultrasound scan – A way of creating an image of the fetus by the use of high
frequency sound waves which are beyond the range of human hearing.
Soft ‘markers’ – Uncommon features seen on scan that can be seen in healthy
babies, but more commonly in babies with chromosomal abnormalities (e.g. Down’s
syndrome).
Chorionic Villus Sampling (CVS) – The removal of small fragments of placental
tissue.
Cordocentesis – Taking a blood sample from the cord before birth with the use of a
needle.
Miscarriage – The loss of the baby before 24 weeks gestation.
Genetics – The study of human inheritance.
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