Chorionic Villus Sampling (CVS) is a very accurate test that is carried out on your unborn baby which can detect chromosomal abnormalities including:
- Down’s Syndrome
- Cystic Fibrosis
- Muscular dystrophy
- Sickle-cell anaemia
- Metabolic disorders
- Specific mental health conditions
A CVS is offered to pregnant women where there is a high risk that the baby may have one of the above conditions, for example a direct relative has suffered or a previous pregnancy had problems or during an earlier antenatal screening test it was suggested that baby may have a problem.
During a CVS, a sample of cells are taken from the placenta and sent to a laboratory to be tested for defects. This may sound similar to an amniocentesis test and a CVS is sometimes offered as an alternative. A CVS can be carried out earlier than an amniocentesis, usually between 10 and 14 weeks which means the results are also received much earlier which will allow you to make any necessary decisions including whether to or not to continue with your pregnancy.
A CVS does carry a slightly higher risk of miscarriage than an amniocentesis test although it is still very low with approximately 2% of women experiencing a miscarriage as a direct result of having a CVS. Before agreeing to the test, you will be able to ask your midwife or doctor any questions that you have about your baby’s safety and the procedure.
What happens during a CVS?
A CVS should take about 20 minutes to complete and most women say that it is not painful but uncomfortable and often compared to the feeling of a smear test.
An ultrasound scan is used before and during the procedure to ensure that you doctor can guide the needle into the placenta safely. There are two ways that the procedure may be carried out and which one is used will depend on the position of your baby and the placenta:
- Transabdominal CVS: Your tummy will be cleaned with antiseptic in order to help prevent infection and a needle will be inserted through your tummy and your abdomen. The needle will be attached to a syringe and this will extract a sample of the cells from your placenta.
- Transcervical CVS: This method of CVS involves the cells being collected through your cervix. Both your vagina and cervix will be cleaned using antiseptic and a tube will be inserted through your vagina and cervix, your doctor will use the ultrasound images to guide the tube to collect cells from the placenta. Suction is then used to remove the cells.
After the test is performed, you will need to be monitored for at least an hour to ensure that you do not suffer from any serious after-effects such as heavy bleeding. After this time, you will be allowed home and advised to rest for at least 24 hours. It is best if you have someone with you whilst travelling home and you should not drive. You should also ensure that you do not carry out any strenuous activity for at least 48 hours.
Most women will suffer from mild cramping and slight spotting or bleeding. However if you have any of the following, you should call your midwife or doctor immediately:
- Heavy bleeding
- High temperature of over 38 degrees
- Leaking clear water from your vagina (not urine)
- You feel shivery
- You feel like you are having contractions
Before leaving the hospital, you will be told how to receive you results and approximately how long you may have to wait. This can vary depending on what you were being tested for. Some results may be returned within a few days while others may take up to three weeks. If the CVS results return to show that baby has an abnormality, you will be offered advice with a specialist who can help you to make the decision about your next steps. Some women decide to terminate their pregnancy, although whatever your decision, your doctor and midwife will fully support you.
by Jenny, mum to William and James