However, people with Down’s syndrome can also have a normal life span and some children are more affected than others.
Why am I having a CVS?
There are many reasons for doing a CVS. These include:
Abnormality seen on ultrasound scan - Pregnant women usually have an ultrasound scan at 12 weeks gestation. This is called a nuchal translucency scan. During the scan we look at the developing baby in your womb and check for an increase in fluid behind the baby’s neck. If an increase is seen, this gives you a higher chance of having a baby with Down’s syndrome. If the ultrasound gives any cause for concern, a CVS can confirm whether the baby has Down’s syndrome.
Age of the mother - All women have a risk of having a baby with Down’s syndrome but the risk increases with age. Older mothers have a higher risk so we may offer you a CVS if you are over 37 years of age.
Previous abnormalities - If you have had a previous pregnancy affected by abnormal chromosomes we may offer you a CVS.
Screening for diseases - We can diagnose many diseases using a CVS. Examples include cystic fibrosis when both parents are cystic fibrosis carriers, or sickle-cell disease from two sickle-cell trait parents.
If you are offered a CVS your obstetrician will counsel you on the possible outcomes. S/he will discuss the various options, including not doing a test, doing a test taking the risks into consideration and what to do in the event of a positive result, including a termination of the pregnancy.
The aim of a CVS is to check your unborn baby for any abnormal chromosomes or inherited conditions. The test is 98% accurate.
The test will confirm whether your baby has an abnormality or not. A normal result will put you and your partner’s minds at rest. An abnormal result will tell you if your baby has Down’s syndrome or some other inherited condition. This would enable you to make a decision to continue with the pregnancy or not. The test results are usually received during early pregnancy so if you decide to terminate the pregnancy it can be done at an early stage.
Are there any alternatives?
An amniocentesis is another test for abnormal chromosomes. In this test we take a sample of the amniotic fluid surrounding your developing baby. This test can be done after 16 weeks gestation. If an abnormality is found on your 12-week ultrasound scan it will be too early for an amniocentesis. A CVS is usually done between 11 and 16 weeks gestation rather than an amniocentesis.
What if you do nothing?
If you do not have the test you will not know if your baby has an abnormality. If you are in a high-risk group we advise having the test.
Author: Dr. Chineze Otigbah MRCOG. Consultant obstetrician and gynaecologist.
© Dumas Ltd 2006