Why have I been offered a test in this pregnancy?

It is possible to diagnose a number of birth defects in pregnancy. These include:

• chromosome abnormalities (e.g. Down syndrome)
• inherited disorders (e.g. Cystic fibrosis).

The early detection of a birth defect allows parents to discuss how they want to manage a pregnancy and cope with the information. It is your decision to have a test or not.

What are some of the reasons that I might choose to have a test?

• Women of 35 years of age or more have an increased risk of having a baby with a chromosome problem, the most common being Down syndrome. Babies with Down syndrome can be born to mothers at any age, although the risk slowly increases when the mother is in her late 30s or over 40. The risk at 35 is sufficient to warrant this test.
• A family history of a chromosome problem. Investigation may show that a prenatal test is appropriate.
• A known disorder in the family which can be passed on to your baby (e.g. cystic fibrosis, muscular dystrophy) is an appropriate reason. There may be specific tests available for the disorder. For these families, genetic counselling and investigation are preferably performed before becoming pregnant.
• If unexpected problems are detected on an ultrasound scan in early pregnancy, further tests may be appropriate. Your doctor, midwife, genetic counsellor or geneticist will discuss the findings with you. Further tests may be offered to help clarify the nature of the problem.

Is Counselling available before I have a test?

Counselling is recommended before any test is performed. This may be carried out by your doctor or a genetic counsellor.

Issues that you might like to discuss include:

• which tests are available and most suitable
• a thorough explanation of the test procedure
• how long results will take and how you will receive them
• the choices available if a problem is detected
• attitudes and personal beliefs about testing and the possible outcomes.

What is Ultrasound?

Ultrasound is high frequency sound that is passed into the body from an ultrasound probe and reflected off the internal organs. An ultrasound machine changes these sound waves into visible images on the screen. Click the ultrasound examination icon for further information.

Chorionic Villus Sampling

CVS allows us to take a small sample of tissue, the chorionic villi, from the developing placenta. CVS is one of the two tests available to check the chromosomes (the structures that contain genes) of the baby. This tissue may also be used for biochemical or direct genetic testing.

CVS is performed at 11 to 12 weeks in the pregnancy and is a day patient procedure.

An ultrasound will be performed first to check how far into your pregnancy you are, to show the position of the baby and to monitor the developing placenta. As the baby is small and not fully developed, very few physical problems can be detected at this stage by ultrasound scan. Your bladder should be full but need not be uncomfortable.

CVS procedure

Chorionic villi can be obtained by inserting a needle through the mother’s abdomen (which has been cleaned with antiseptic and numbed with anaesthetic) under ultrasound guidance into the developing placenta. A small sample of chorionic villi is withdrawn.

• The chorion villus sample is sent to the laboratory for testing.
• A chromosome result will be available in one to two weeks.
• A biochemical or direct genetic (DNA) test may take longer.

CVS carries a small risk of causing a miscarriage. The average risk is up to one chance in 100.

The chromosome test establishes the sex of the baby and if you wish to know this information you must ask the person who gives you your result.

Amniocentesis (Amnio)

What is Amniocentesis (Amnio)?

Amniocentesis is the removal of a small amount of amniotic fluid from the sac around the baby.

This fluid contains cells which come from the baby and the placenta. This test is usually performed at 16 weeks into the pregnancy.

Amnio Procedure

After cleaning the skin with antiseptic, a fine needle is inserted under ultrasound guidance through the mother’s abdomen into a pool of amniotic fluid. A small amount of fluid is withdrawn and the needle removed. The amniotic fluid is sent to the laboratory for testing. A chromosome result will take two to three weeks. A biochemical or direct genetic (DNA) test may take longer.

The chromosome test establishes the sex of the baby and if you wish to know this information you must ask the person who gives you the result.

Amniocentesis carries a small risk of causing a miscarriage. The average risk is up to one chance in 100.

Are the procedures painful?

Most women say amniocentesis is not painful. Some women, however, feel discomfort. Some women experience discomfort during and after CVS.

For both tests it is advisable to rest for the remainder of the day. You may like to have your partner, a family member or friend with you on the day of the test.

Another popular idea is to bring along a hand-held CD player or “walkman” with earphones to help you relax with some quiet music.

What will happen after the test?

There is a risk of naturally occurring miscarriage in all pregnancies. The risk is highest in early pregnancy and increases with the age of the mother. The risks quoted for prenatal tests are in addition to this naturally occurring risk of miscarriage.

Most people have normal results after the test. However, if the test shows the baby to have a problem, you will have the opportunity to discuss the results with your doctor, genetic counsellor or geneticist.

It is important to realise that while the combination of ultrasound scan and CVS or amniocentesis goes a long way towards identifying your baby as normal, it does not guarantee that every possible abnormality has been excluded.

What is the philosophy of Mater Mothers’ Hospital?

Antenatal testing is routinely undertaken in all major obstetric-maternity hospitals. We, too, offer this service to women who may have concerns that the unborn baby is at risk of suffering from some major abnormality. We offer the test in the hope that these concerns can be alleviated, or that something can be done to help the baby while still in the uterus, at the time of delivery or immediately after the birth.

In keeping with Catholic Church teaching and the philosophy of the Hospital, termination of pregnancy is not provided at Mater Mothers’ Hospital. We do offer a full range of pastoral care, ethical advice and counselling support to supplement medical and nursing services to all women and their families. Please ask one of the staff to help you arrange an appointment if you would like to access these services.