Antenatal Tests

There are currently three diagnostic tests available which look at the baby's genetic make-up:

Amniocentesis

Taking a sample of fluid from around the baby.

Fetal Blood Sampling

Taking a sample of blood directly from the baby.

Chorionic Villus Sampling

Taking a sample of the placenta.

Amniocentesis

This is the most commonly used diagnostic genetic test as it has the lowest rate of miscarriage (0.5 - 1%)
A fine needle is guided, by scan, through the abdominal wall into the uterus where a sample of fluid from around the baby is taken.
The skin cells shed by the baby into the fluid are grown (cultured) and examined to give the chromosomes (genetic make-up) of the baby.
An initial result will be available within 2 - 3 days which looks for the three major chromosome abnormalities, Down's syndrome, Edwards' syndrome and Patau's syndrome.
The complete test results will take 2 - 3 weeks.

Fetal Blood Sample

This test has a slightly higher rate of miscarriage (1%) than amniocentesis.
A fine needle is guided, by scan, through the abdominal wall into the uterus where a sample of blood is taken from the umbilical cord or from a small blood vessel in the baby's abdomen.
This test has the advantage of the complete result being available in 5 - 7 days.

Chorionic Villus Sampling

This test is rarely used, but on occasions where there is very little fluid around the baby, it may be the preferred option.
The miscarriage rate is 1 - 2%.
A fine needle is guided, by scan, through the abdominal wall into the placenta where a small sample is removed.
An initial result will be available within 2 - 3 days which looks for the three major chromosome abnormalities, Down's syndrome, Edwards' syndrome and Patau's syndrome.
The complete test results take 1 - 2 weeks.

All of these tests carry a risk of miscarriage and it is therefore extremely important that parents are encouraged to think through the implications of what they would do with the additional information.

Talk to your midwife or obstetrician to see what would be the most appropriate test, if any, for you.

What is the advantage of having a test?

Every couple will need to think through the reason why they might want to choose to have a test. Some considerations are explored below.

Some parents feel that they need to know whether the heart problem in their baby is part of a genetic syndrome, such as Down's syndrome, as this additional information may help them choose the way forward.

There are certain serious genetic conditions which may mean that the baby will not survive pregnancy or live for long after birth and parents may be advised that the option for surgery would not be in the baby's best interest.

For some parents, knowing their baby has a genetic syndrome in addition to a major heart abnormality, may help them with the difficult decision of whether or not to continue with the pregnancy.

Other parents choose to have a genetic test in order to obtain as complete a picture of their baby's problems as possible, so that they can prepare themselves and their families during the remainder of the pregnancy.

Further Sources of Support and Information

Antenatal Results and Choices (ARC) is a national charity which offers non-directive support and information, throughout the antenatal testing process, to parents seeking a greater understanding of the antenatal treatment options available to them.

ARC offers a telephone helpline, an email support group and a series of publications, for which you may incur a small charge.